Dictionary of Options

Dictionary of Options

This chapter provides detailed descriptions of options that you can specify in the following chart statements:

BOXCHART
CCHART
IRCHART
MCHART
MRCHART
NPCHART
PCHART
RCHART
SCHART
UCHART
XCHART
XRCHART
XSCHART

Options are specified after the slash (/) in a chart statement. For example, to request tests for special causes with an $\bar{X}$ and R chart, you can use the TESTS= option as follows:

   proc shewhart data=measures;
      xrchart length*sample / tests=1 to 4 ;
   run;

The options described in this chapter are listed alphabetically. For tables of options organized by function, see the "Summary of Options" sections in the chapters for the various chart statements.

Unless indicated otherwise, the options listed here are available with every chart statement. For statements that create two charts, the term primary chart refers to the upper chart (for instance, the $\bar{X}$ chart created with the XRCHART statement), and the term secondary chart refers to the lower chart (for instance, the R chart created with the XRCHART statement). The term primary chart also refers to the single chart created by some statements (for instance, the p chart created with the PCHART statement).

ALLLABEL=VALUE

ALLLABEL=(variable)

labels every point on the primary chart with the VALUE plotted for that subgroup or with the value of a variable in the input data set.

The variable provided in the input data set can be numeric or character. If the variable is a character variable, its length cannot exceed 16. For each subgroup of observations, the formatted value of the variable in the observations is used to label the point representing the subgroup. If you are reading a DATA= data set with multiple observations per subgroup, the values of the variable should be identical for observations within a subgroup. You should use this option with care to avoid cluttering the chart. By default, points are not labeled. Related options are CFRAMELAB=, OUTLABEL=, LABELFONT=, LABELHEIGHT=, and TESTLABEL=, but note that the OUTLABEL= option cannot be specified with the ALLLABEL= option.

ALLLABEL2=VALUE

ALLLABEL2=(variable)

labels every point on the secondary chart with the VALUE plotted for that subgroup or with the value of a variable in the input data set.

The variable provided in the input data set can be numeric or character. If the variable is a character variable, its length cannot exceed 16. For each subgroup of observations, the formatted value of the variable in the observations is used to label the point representing the subgroup. If you are reading a DATA= data set with multiple observations per subgroup, the values of the variable should be identical for observations within a subgroup. You should use this option with care to avoid cluttering the chart. By default, points are not labeled. Related options are CFRAMELAB=, OUTLABEL2=, LABELFONT=, LABELHEIGHT=, and TESTLABEL2=, but note that the OUTLABEL2= option cannot be specified with the ALLLABEL2= option. The option is available in the IRCHART, MRCHART, RCHART, SCHART, XRCHART, and XSCHART statements and in the BOXCHART, MCHART, and XCHART statements with the TRENDVAR= option.

ALLN

plots summary statistics for all subgroups, regardless of whether the subgroup sample size equals the nominal control limit sample size n specified by the LIMITN= option or the variable _LIMITN_ in the LIMITS= data set. Use the ALLN option in conjunction with the LIMITN= option or the variable _LIMITN_.

The ALLN option is useful in applications where almost all of the subgroups have a common sample size n, and you want to display fixed (rather than varying) control limits corresponding to the nominal sample size n. The disadvantage of using the ALLN option with widely differing subgroup sample sizes is that the interpretation of the control limits is meaningful only for those subgroups whose sample size is equal to n. To request special symbol markers indicating that not all the sample sizes are equal to n, use the NMARKERS option in conjunction with the ALLN option.

The ALLN option is not available in the IRCHART statement.

ALPHA=value

requests probability limits. If you specify ALPHA= $\alpha$ , the control limits are computed so that the probability is $\alpha$ that a subgroup summary statistic exceeds its control limits. This assumes that the process is in statistical control and that the data follow a certain theoretical distribution, which depends on the chart statement. The Poisson distribution is assumed for the CCHART and UCHART statements, and the binomial distribution is assumed for the NPCHART and PCHART statements. The normal distribution is assumed for all other chart statements. For the equations used to compute probability limits, see the "Details" section in the chapter for the chart statement that you are using.

The value of $\alpha$ can range between 0 and 1 for most statements. However, for the MCHART statement, the MRCHART statement, and the BOXCHART statement with the CONTROLSTAT=MEDIAN option, the value of $\alpha$ must be one of the following: 0.001, 0.002, 0.01, 0.02, 0.025, 0.04, 0.05, 0.10, or 0.20.

Note the following:

As an alternative to specifying ALPHA= $\alpha$ , you can read $\alpha$ from the variable _ALPHA_ in a LIMITS= data set by specifying the READALPHA option. See "Input Data Sets" in the chapter for the chart statement in which you are interested.
As an alternative to specifying ALPHA= $\alpha$ (or reading the variable _ALPHA_ from a LIMITS= data set), you can request " $k\sigma$ control limits" by specifying SIGMAS=k (or reading the variable _SIGMAS_ from a LIMITS= data set).

If you specify neither the ALPHA= option nor the SIGMAS= option, the procedure computes $3\sigma$ control limits by default.

ANNOTATE=SAS-data-set

ANNO=SAS-data-set

[Graphics]
specifies an ANNOTATE= type data set, as described in SAS/GRAPH Software: Reference, that enhances a primary chart. The ANNOTATE= data set specified in a chart statement enhances all charts created by that particular statement. You can also specify an ANNOTATE= data set in the PROC SHEWHART statement to enhance all primary charts created by the procedure.

ANNOTATE2=SAS-data-set

ANNO2=SAS-data-set

[Graphics]
specifies an ANNOTATE= type data set, as described in SAS/GRAPH Software: Reference, that enhances a secondary chart. The ANNOTATE2= data set specified in a chart statement enhances all charts created by that particular statement. You can also specify an ANNOTATE2= data set in the PROC SHEWHART statement to enhance all secondary charts created by the procedure.

This option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements and in the BOXCHART, MCHART, and XCHART statements with the TRENDVAR= option.

BILEVEL

arranges the Shewhart chart in two levels (rather than the default of one level) so that twice as much data can be displayed on a page or screen. The second level is a continuation of the first level, and this arrangement is continued on subsequent pages until all the subgroups are displayed. You use the NPANELPOS= option to control the number of subgroup positions in each level. If you specify the BILEVEL option in a chart statement that produces primary and secondary charts, you must also specify the SEPARATE option.

BLOCKLABELPOS=ABOVE | LEFT | RIGHT

specifies the position of a block-variable label in the block legend. As shown in Figure 46.1, the keyword ABOVE places the label immediately above the legend, LEFT places the label to the left of the legend, and RIGHT places the label to the right of the legend. Use the keywords LEFT and RIGHT with labels that are short enough to fit in the margins on each side of the chart; otherwise, they will be truncated. Use the keyword RIGHT only when the legend is below the control chart (BLOCKPOS=3 or BLOCKPOS=4). The default keyword is ABOVE. Related options are BLOCKLABTYPE=, BLOCKREP, BLOCKPOS=, CBLOCKVAR=, and CBLOCKLAB=.

Figure 46.1: Positions for block-variable Labels

BLOCKLABTYPE=SCALED | TRUNCATED

BLOCKLABTYPE=height

[Graphics]
specifies how lengthy block variable values are to be treated when there is insufficient space to display them in the block legend. If you specify the BLOCKLABTYPE=SCALED option, the values are uniformly reduced in height so that they fit. If you specify the BLOCKLABTYPE=TRUNCATED option, lengthy values are truncated on the right until they fit. You can also specify a text height in vertical percent screen units for the values. By default, lengthy values are not displayed. Related options are BLOCKLABELPOS=, BLOCKREP, BLOCKPOS=, CBLOCKVAR=, and CBLOCKLAB=.

BLOCKPOS=n

specifies the vertical position of the legend for the values of the block-variables (see "Displaying Stratification in Blocks of Observations" ). Values of n and the corresponding positions are as follows. By default, BLOCKPOS=1.

n	Legend Position
1	Top of chart, offset from axis frame
2	Top of chart, immediately above axis frame
3	Bottom of chart, immediately above horizontal axis
4	Bottom of chart, below horizontal axis label

Figure 46.1 illustrates the various positions that can be specified.

Figure 46.2: Positions for block-variable Legends

Related options are BLOCKLABELPOS=, BLOCKLABTYPE=, BLOCKREP, CBLOCKVAR=, and CBLOCKLAB=.

BLOCKREP: specifies that block variable values for all subgroups are to be displayed. By default, only the first block variable value in any block is displayed, and repeated block variable values are not displayed. Related options are BLOCKLABELPOS=, BLOCKLABTYPE=, BLOCKPOS=, CBLOCKVAR=, and CBLOCKLAB=. For more information on block variables, see "Displaying Stratification in Blocks of Observations" .
BOXCONNECT
BOXCONNECT=MEAN | MEDIAN | MAX | MIN | Q1 | Q3: specifies that the points representing subgroup means, medians, maximum values, minimum values, first quartiles or third quartiles in box-and-whisker plots created with the BOXCHART statement are to be connected. If BOXCONNECT is specified without a keyword identifying the points to be connected, subgroup means are connected. By default, no points are connected. The BOXCONNECT option is available only in the BOXCHART statement.
BOXSTYLE=keyword: specifies the style of the box-and-whisker plots that are displayed for subgroup samples by the BOXCHART statement.

The keywords SKELETAL, SCHEMATIC, SCHEMATICID, and SCHEMATICIDFAR are useful for creating conventional box-and-whisker displays. The keywords POINTS, POINTSJOIN, POINTSBOX, POINTSID, and POINTSJOINID are used to generalize the BOXSTYLE= option and, in particular, to facilitate the creation of so-called "multi-vari" charts, as illustrated in Output 32.7.2 and Output 32.7.3.

If you specify BOXSTYLE=SKELETAL, the whiskers are drawn from the edges of the box to the extreme values of the subgroup sample. This plot is sometimes referred to as a skeletal box-and-whisker plot. By default, the whiskers are drawn without serifs, but you can add serifs with the SERIFS option. Figure 46.3 illustrates the elements of a typical skeletal boxplot.

Figure 46.3: BOXSTYLE= SKELETAL

If you specify BOXSTYLE=SCHEMATIC, a whisker is drawn from the upper edge of the box to the largest value within the upper fence and from the lower edge of the box to the smallest value within the lower fence. Figure 46.4 illustrates a typical schematic boxplot and the locations of the fences (which are not displayed in actual output). Serifs are added to the whiskers by default. Observations outside the fences are identified with a special symbol; you can specify the shape and color for this symbol with the IDSYMBOL= and IDCOLOR= options. The default symbol is a square. This type of plot corresponds to the schematic box-and-whisker plot described in Chapter 2 of Tukey (1977).

If you specify BOXSTYLE=SCHEMATICID, a schematic box-and-whisker plot is displayed in which the value of the first variable listed in the ID statement is used to label the symbol marking each observation outside the upper and lower fences.

If you specify BOXSTYLE=SCHEMATICIDFAR, a schematic box-and-whisker plot is displayed in which the value of the first variable listed in the ID statement is used to label the symbol marking each observation outside the lower and upper far fences. The lower and upper far fences are located 3×IQR below the 25^th percentile and above the 75^th percentile, respectively. Observations between the fences and the far fences are identified with a symbol but are not labeled with the ID variable.

Figure 46.4: BOXSTYLE= SCHEMATIC

NOTE: To make side-by-side box charts (as opposed to a control chart with subgroup box plots), you should use the BOXCHART statement with the NOLIMITS option in addition to the BOXSTYLE= option.

If you specify BOXSTYLE=POINTS, all the values in the subgroup sample are plotted as points, and neither a box nor whiskers are drawn. By default, a square plotting symbol is used for the values. You can specify a symbol with the IDSYMBOL= option. You can specify the color of the symbols with the IDCOLOR= option (the default color is the color specified with the CBOXES= option or the second color in the device color list).

If you specify BOXSTYLE=POINTSJOIN, all the values in the subgroup sample are plotted as points joined with a vertical line. Neither a box nor whiskers are drawn. See Output 32.7.2 for an illustration. By default, a square plotting symbol is used for the values. You can specify a symbol with the IDSYMBOL= option, and you can specify the color of the symbol with the IDCOLOR= option. You can specify the color of the vertical line with the CBOXES= option.

If you specify BOXSTYLE=POINTSBOX, all the values in the subgroup sample are plotted as points enclosed in a box. By default, a square plotting symbol is used for the values. You can specify a symbol with the IDSYMBOL= option, and you can specify the color of the symbol with the IDCOLOR= option. You can specify the color of the box with the CBOXES= option, the fill color of the box with the CBOXFILL= option, and the line type of the box with the LBOXES= option.

If you specify BOXSTYLE=POINTSID, all the values in the subgroup sample are plotted using labels specified as the values of the first variable in the ID statement. See Output 32.7.3 for an illustration. It is recommended that you use single-character labels. You can specify a font for the labels with the IDFONT= option. You can specify the height of the labels with the IDHEIGHT= option. You can specify the color of the labels with the IDCTEXT= option.

If you specify BOXSTYLE=POINTSJOINID, all the values in the subgroup sample are plotted using labels specified as the values of the first variable in the ID statement, and the values are joined by a vertical line. It is recommended that you use single-character labels. You can specify a font for the labels with the IDFONT= option. You can specify the height of the labels with the IDHEIGHT= option. You can specify the color of the labels with the IDCTEXT= option, and you can specify the color of the vertical line with the CBOXES= option.

The BOXSTYLE= option is available only in the BOXCHART statement; see Example 32.2. The styles SCHEMATIC, SCHEMATICID, and SCHEMATICIDFAR are available only when the input data set is a DATA= data set. By default, BOXSTYLE=SKELETAL. Related options include BOXWIDTH=, BOXWIDTHSCALE=, IDCOLOR=, and IDSYMBOL=.

Note that the keywords POINTS, POINTSJOIN, POINTSBOX, POINTSID, and POINTSJOINID for the BOXSTYLE= option can be used in conjunction with the CPHASEBOX=, CPHASEBOXFILL=, CPHASEBOXCONNECT=, CPHASEMEANCONNECT=, and PHASEMEANSYMBOL= options to create "multi-vari" displays.

BOXWIDTH=value

[Graphics]
specifies the width (in horizontal percent screen units) of box-and-whisker plots created with the BOXCHART statement. The default width is chosen so that the boxes are as wide as possible without colliding. You should use the BOXWIDTH= option in situations where the number of subgroups per panel is very small and you want to reduce the width. The BOXWIDTH= option is available only in the BOXCHART statement.

BOXWIDTHSCALE=value

[Graphics]
specifies that the width of box-and-whisker plots created with the BOXCHART statement is to vary proportionately to a particular function of the subgroup sample size n. The function is determined by the value and is identified on the chart with a legend.

If you specify a positive value, the widths are proportional to n^value. In particular, if you specify BOXWIDTHSCALE=1, the widths are proportional to the sample size. If you specify BOXWIDTHSCALE=0.5, the widths are proportional to $\sqrt{n}$ , as described by McGill and others (1978). If you specify BOXWIDTHSCALE=0, the widths are proportional to log(n). See Example 32.4 for an illustration of the BOXWIDTHSCALE= option.

By default, the box widths are constant. The BOXWIDTHSCALE= option is available only in the BOXCHART statement.

CAXIS=color

CAXES=color

CA=color

[Graphics]
specifies the color for the axes and tick marks. This option overrides any COLOR= specifications in an AXIS statement. The default is the first color in the device color list.

CBLOCKLAB=color

[Graphics]
specifies a fill color for the frame that encloses the block-variable label in a block legend. By default, this area is not filled. Related options are BLOCKLABELPOS=, BLOCKLABTYPE=, BLOCKREP, BLOCKPOS=, and CBLOCKVAR=.

CBLOCKVAR=variable | (variable-list)

[Graphics]
specifies variables whose values are colors for filling the background of the legend associated with block-variables. Each CBLOCKVAR= variable must be a character variable of no more than eight characters in the input data set (a DATA=, HISTORY=, or TABLE= data set). A list of CBLOCKVAR= variables must be enclosed in parentheses.

The procedure matches the CBLOCKVAR= variables with block-variables in the order specified. That is, each block legend will be filled with the color value of the CBLOCKVAR= variable of the first observation in each block. In general, values of the i^th CBLOCKVAR= variable are used to fill the block of the legend corresponding to the i^th block-variable. For examples of the CBLOCKVAR= option, see Figure 47.4 and Figure 47.5.

By default, fill colors are not used for the block-variable legend. The CBLOCKVAR= option is available only when block-variables are used in the chart statement.

CBOXES=color

CBOXES=(variable)

[Graphics]
specifies the colors for the outlines of the box-and-whisker plots created with the BOXCHART statement. You can use one of the following approaches:

You can specify CBOXES=color to provide a single outline color for all the box-and-whisker plots.
You can specify CBOXES=(variable) to provide a distinct outline color for each box-and-whisker plot as the value of the variable. The variable must be a character variable of length 8 less in the input data set, and its values must be valid SAS/GRAPH color names. The outline color of the plot displayed for a particular subgroup is the value of the variable in the observations corresponding to this subgroup. Note that if there are multiple observations per subgroup in the input data set, the values of the variable should be identical for all the observations in a given subgroup.

The default color is the second color in the device color list. The CBOXES= option is available only in the BOXCHART statement.

CBOXFILL=color

CBOXFILL=(variable)

[Graphics]
specifies the interior fill colors for the box-and-whisker plots created with the BOXCHART statement. You can use one of the following approaches:

You can specify CBOXFILL=color to provide a single color for all of the box-and-whisker plots.
You can specify CBOXFILL=(variable) to provide a distinct color for each box-and-whisker plot as the value of the variable. The variable must be a character variable of length 8 or less in the input data set, and its values must be valid SAS/GRAPH color names (or the value EMPTY, which you can use to suppress color filling). The interior color of the plot displayed for a particular subgroup is the value of the variable in the observations corresponding to this subgroup. Note that if there are multiple observations per subgroup in the input data set, the values of the variable should be identical for all the observations in a given subgroup.

By default, the interiors are not filled. The CBOXFILL= option is available only in the BOXCHART statement.

CCLIP=color

[Graphics]
specifies a color for the plotting symbol that is specified with the CLIPSYMBOL= option to mark clipped points. The default color is the color specified in the COLOR= option in the SYMBOL1 statement.

CCONNECT=color

[Graphics]
specifies the color for the line segments connecting points on the chart. The default color is the color specified in the COLOR= option in the SYMBOL1 statement. This option is not applicable in the BOXCHART statement unless you also specify the BOXCONNECT option.

CFRAME=color

CFRAME=(color-list)

[Graphics]
specifies the colors for filling the rectangle enclosed by the axes and the frame. By default, this area is not filled. The CFRAME= option cannot be used in conjunction with the NOFRAME option.

You can specify a single color to fill the entire area. Alternatively, if you are displaying phases (blocks) of data read with the READPHASES= option, you can specify a color-list with the CFRAME= option to fill the sub-rectangles of the framed area corresponding to the phases. The colors, in order of specification, are applied to the sub-rectangles starting from left to right. You can use the value EMPTY in the color-list to avoid filling a particular sub-rectangle. If the number of colors is less than the number of phases, the colors are applied cyclically. The colors are also used for phase legends requested with the PHASELEGEND option.

CFRAMELAB=color

[Graphics]
specifies the color for filling rectangles that frame the point labels displayed with the ALLLABEL=, ALLLABEL2=, OUTLABEL=, and OUTLABEL2= options. By default, the points are not framed.

CHREF=color

[Graphics]
specifies the color for the lines requested by the HREF=and HREF2= options. The default is the first color in the device color list.

CIINDICES <(<TYPE=keyword><ALPHA=value>)>

requests capability index confidence limits based on subgroup summary data. The confidence limit values calculated are approximate.

TYPE=keyword: specifies the type of confidence limit. Valid values are LOWER, UPPER and TWOSIDED. The default value is TWOSIDED.
ALPHA=value: specifies the default confidence level to compute confidence limits. The percentage for the confidence limits is (1-value) * 100. For example, ALPHA=.05 results in a 95% confidence limit. The default value is .05 and the possible range of values is from 0 to 1.

CINFILL=color

[Graphics]
specifies the color for the area inside the upper and lower control limits. By default, this area is not filled with a color. See also the COUTFILL= option.

CLIMITS=color

[Graphics]
specifies the color for the control limits, the central line, and the labels for these lines. The default color is the first color in the device color list.

CLIPCHAR='character'

[Line Printer]
specifies a plot character that identifies clipped points, as requested with the CLIPFACTOR= option. Specifying the CLIPCHAR= option is recommended when the CLIPFACTOR= option is used. The default character is an asterisk (*).

CLIPFACTOR=factor

requests clipping of extreme points on the control chart. The factor that you specify determines the extent to which these values are clipped, and it must be greater than one (useful values are in the range 1.5 to 2).

For examples of the CLIPFACTOR= option, see Figure 47.28 and Figure 47.29. The CLIPFACTOR= option should not be used in any statement in which the STARVERTICES= option is also used. Related clipping options are CCLIP=, CLIPCHAR=, CLIPLEGEND=, CLIPLEGPOS=, CLIPSUBCHAR=, and CLIPSYMBOL=.

CLIPLEGEND='label'

specifies the label for the legend that indicates the number of clipped points when the CLIPFACTOR= option is used. The label must be no more than 16 characters and must be enclosed in quotes. For an example, see Figure 47.29.

CLIPLEGPOS=TOP | BOTTOM

specifies the position for the legend that indicates the number of clipped points when the CLIPFACTOR= option is used. The keywords TOP and BOTTOM position the legend at the top or bottom of the chart, respectively. Do not specify CLIPLEGPOS=TOP together with the PHASELEGEND option or the BLOCKPOS=1 or BLOCKPOS=2 options. By default, CLIPLEGPOS=BOTTOM.

CLIPSUBCHAR='character'

specifies a substitution character (such as #) for the label provided with the CLIPLEGEND= option. The substitution character is replaced with the number of points that are clipped. For example, suppose that the following statements produce a chart in which three extreme points are clipped:

   proc shewhart data=pistons;
      xrchart diameter*hour /
         clipfactor  = 1.5
         cliplegend  = 'Points clipped=#'
         clipsubchar = '#' ;
   run;

Then the clipping legend displayed on the chart will be

   Points clipped=3

CLIPSYMBOL=symbol

[Graphics]
specifies a plot symbol used to identify clipped points on the chart and in the legend when the CLIPFACTOR= option is used. You should use this option in conjunction with the CLIPFACTOR= option. The default symbol is CLIPSYMBOL=SQUARE.

CLIPSYMBOLHT=value

specifies the height for the symbol marker used to identify clipped points on the chart when the CLIPFACTOR= option is used. The default is the height specified with the H= option in the SYMBOL statement.

For general information about clipping options, refer to "Clipping Extreme Points".

CNEEDLES=color

[Graphics]
requests that points are to be connected to the central line with vertical line segments (needles) and specifies the color of the needles. You can use needles to visually represent the process as a series of shocks or vertical displacements away from a constant mean. See Figure 47.26 for an example. The default color is the second color in the device color list. The CNEEDLES= option is available in all chart statements except the BOXCHART statement.

CONNECTCHAR='character'

CCHAR='character'

[Line Printer]
specifies the character used to form line segments that connect points on a chart. The default character is a plus (+) sign.

CONTROLSTAT=MEAN | MEDIAN

specifies whether the control limits displayed in a box chart are to be computed for subgroup means or for subgroup medians. By default, CONTROLSTAT=MEAN. The CONTROLSTAT= option is available only in the BOXCHART statement.

COUT=color

[Graphics]
specifies the color for the plotting symbols and the portions of connecting line segments that lie outside the control limits. The default color is the second color in the device color list. This option is useful for highlighting out-of-control points.

COUTFILL=color

[Graphics]
specifies the fill color for the areas outside the control limits that lie between the connected points and the control limits and are bounded by connecting lines. This option is useful for highlighting out-of-control points. See Figure 49.11 for an example. By default, these areas are not filled. Note that you can use the CINFILL= option to fill the area inside the control limits.

CPHASEBOX=color

specifies the color for a box that encloses all of the plotted points for a phase (group of consecutive observations that have the same value of the variable _PHASE_). By default, an enclosing box is not drawn.

CPHASEBOXFILL=color

specifies the fill color for a box that encloses all of the plotted points for a phase. By default, an enclosing box is not drawn.

CPHASEBOXCONNECT=color

specifies the color for line segments that connect the vertical edges of adjacent enclosing boxes requested with the CPHASEBOX= option or the CPHASEBOXFILL= option. The vertical coordinates of the attachment points represent the average of the values plotted inside the box. The CPHASEBOXCONNECT= option is an alternative to the CPHASEMEANCONNECT= option.

CPHASELEG=color

[Graphics]
specifies a text color for the phase labels requested with the PHASELEGEND option. By default, if you specify a list of fill colors with the CFRAME= option, these colors are used for the corresponding phase labels, otherwise, the CTEXT= color is used for the phase labels.

CPHASEMEANCONNECT=color

specifies the color for line segments that connect points representing the average of the values plotted within a phase. This option must be used in conjunction with the CPHASEBOX= or CPHASEBOXFILL= options, and it is an alternative to the CPHASEBOXONNECT= option. The points are centered horizontally within the enclosing boxes.

CSTARCIRCLES=color

[Graphics]
specifies a color for the circles requested with the STARCIRCLES= option. See the "Displaying Auxiliary Data with Stars" section. By default, the color specified with the CSTARS= option is used.

CSTARFILL=color

CSTARFILL=(variable)

[Graphics]
specifies a color or colors for filling the interior of stars requested with the STARVERTICES= option. You can use one of the following approaches:

Specify a single color to be used for all stars with CSTARFILL=color.
Specify a distinct color for each star (or subsets of stars) by providing the colors as values of a variable specified with CSTARFILL=(variable). The variable must be a character variable of length 8 or less in the input data set, and its values must be valid SAS/GRAPH colors or the value EMPTY. The color for the star positioned at the i^th subgroup on the chart is the value of the CSTARFILL= variable in the observations corresponding to the i^th subgroup. Note that if there are multiple observations per subgroup in the input data set (for instance, if you are using the XRCHART statement in the SHEWHART procedure to analyze observations from a DATA= input data set), the values of the CSTARFILL= variable should be identical for all the observations in a given subgroup.

See "Displaying Auxiliary Data with Stars" . By default, the interior of the stars is empty.

CSTAROUT=color

[Graphics]
specifies a color for those portions of the outlines of stars (requested with the STARVERTICES= option) that exceed the inner or outer circles. This option applies only with the STARTYPE=RADIAL and STARTYPE=SPOKE options, and it is useful for highlighting extreme values of star vertex variables. See "Displaying Auxiliary Data with Stars" .

CSTARS=color

CSTARS=(variable)

[Graphics]
specifies a color or colors for the outlines of stars requested with the STARVERTICES= option.

You can use one of the following approaches:

You can specify a single color to be used for all the stars on the chart with CSTARS=color.
You can specify a distinct outline color for each star (or subsets of stars) by providing the colors as values of a variable specified with CSTARS=(variable). The variable must be a character variable of length 8 or less in the input data set. The outline color for the star positioned at the i^th subgroup on the chart is the value of the CSTARS=variable in the observations corresponding to the i^th subgroup. Note that if there are multiple observations per subgroup in the input data set (for instance, if you are using the XRCHART statement in the SHEWHART procedure to analyze observations from a DATA= input data set), the values of the CSTARS= variable should be identical for all the observations in a given subgroup.

See "Displaying Auxiliary Data with Stars" . By default, the second color in the device color list is used.

CSYMBOL='label'

CSYMBOL=C | CBAR | CPM | CPM2 | C0

specifies a label for the central line in a c chart. You can use the option in two ways:

You can specify a quoted label of length 16 or less.

You can specify one of the keywords listed in the following table. Each keyword requests a label of the form symbol=value, where symbol is the symbol given in the table, and value is the value of the central line. If the central line is not constant, only the symbol is displayed.

	Symbol Printed on Charts Produced by
Keyword	Graphics Devices	Line Printers
C	C	C
CBAR	$\overline{C}$	$\overline{C}$
CPM	C'	C'
CPM2	C^''	C^''
C0	C₀	C0

See Example 33.2 for an example. The default keyword is CBAR. The CSYMBOL= option is available only in the CCHART statement.

CTESTS=color | test-color-list

CTEST=color | test-color-list

[Graphics]
specifies colors for labels indicating points where a test is positive.

You can specify the color for the labels used to identify points at which tests for special causes specified in the TESTS= option are positive. For Tests 2 through 8, this color is also used for the line segments that connect patterns of points for which a test is positive. The default color is the second color in the device color list.
You can specify the test-color-list to allow different colors to be used for the labels and highlighted line segments associated with different tests for special causes. Any positive tests for which no specific CTESTS= value is specified are displayed using the general CTESTS= color. A non-default general CTESTS= color can be specified using the CTESTS=color syntax.

The following options request the standard tests for special causes 1 through 4 and one user-defined test designated B.

   TESTS  = 1 to 4 M(K=4 DIR=DEC Code=B);
   CTESTS = green;
   CTESTS = (1 purple 3 yellow B blue);

Test 1 will be displayed in purple, Test 3 in yellow, and Test B in blue. Tests 2 and 4 will be displayed in green, the general CTESTS= color.

CTEXT=color

[Graphics]
specifies the color for tick mark values and axis labels. This color is also used for the sample size legend and for the control limit legend. The default color is the color specified in the CTEXT= option in the most recent GOPTIONS statement.

CVREF=color

CV=color

[Graphics]
specifies the color for reference lines requested by the VREF= and VREF2= options. The default is the first color in the device color list.

CZONES=color

[Graphics]
requests lines marking zones A, B, and C for the tests for special causes (see the TESTS= option) and specifies the color for these lines. This color is also used for labels requested with the ZONELABELS option. The default color is the first color in the device color list.

DATAUNIT=PERCENT | PROPORTION

allows you to use proportions or percents as the values for processes when you are using the PCHART or NPCHART statements and reading a DATA= input data set. Specify DATAUNIT=PERCENT to indicate that the values are percents of nonconforming items. Specify DATAUNIT=PROPORTION to indicate that the values are proportions of nonconforming items. Values for percents can range from 0 to 100, while values for proportions can range from 0 to 1. By default, the values of processes read from a DATA= data set for PCHART and NPCHART statements are assumed to be numbers (counts) of nonconforming items. The DATAUNIT= option is available only in the NPCHART and PCHART statements.

DESCRIPTION='string'

DES='string'

[Graphics]
specifies a description for the primary chart of length 40 or less that appears in the PROC GREPLAY master menu. The default string is the variable name. A related option is NAME=.

DESCRIPTION2='string'

DES2='string'

[Graphics]
specifies a description for the secondary chart of length 40 or less that appears in the PROC GREPLAY master menu. The default string is the variable name. The DESCRIPTION2= option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements, and it is used in conjunction with the SEPARATE option. A related option is NAME2=.

ENDGRID

adds a grid to the rightmost portion of the chart, beginning with the first labeled major tick mark position that follows the last plotted point. This grid is useful in situations where you want to add points by hand after the chart is created. You can use the HAXIS= option to force space to be added to the horizontal axis.

EXCHART

creates a control chart only when exceptions occur, specifically, when the control limits are exceeded or when any of the tests requested with the TESTS= option or the TESTS2= option are positive.

FONT=font

[Graphics]
specifies a software font for labels and legends. You can also specify fonts for axis labels in an AXIS statement. The FONT= font takes precedence over the FTEXT= font specified in the GOPTIONS statement. Hardware characters are used by default.

GRID

adds a grid to the control chart. Grid lines are horizontal lines positioned at labeled major tick marks, and they cover the length and height of the plotting area.

HAXIS=values

HAXIS=AXISn

specifies tick mark values for the horizontal (subgroup) axis. If the subgroup variable is numeric, the values must be numeric and equally spaced. Numeric values can be given in an explicit or implicit list. If the subgroup variable is character, values must be quoted strings of length 16 or less. If a date, time, or datetime format is associated with a numeric subgroup variable, SAS datetime literals can be used. Examples of HAXIS= lists follow:

   haxis=0 2 4 6 8 10
   haxis=0 to 10 by 2
   haxis='LT12A' 'LT12B' 'LT12C' 'LT15A' 'LT15B' 'LT15C'
   haxis='20MAY88'D to '20AUG88'D by 7
   haxis='01JAN88'D to '31DEC88'D by 30

If the subgroup variable is numeric, the HAXIS= list must span the subgroup variable values, and if the subgroup variable is character, the HAXIS= list must include all of the subgroup variable values. You can add subgroup positions to the chart by specifying HAXIS= values that are not subgroup variable values.

If you specify a large number of HAXIS= values, some of these may be thinned to avoid collisions between tick mark labels. To avoid thinning, use one of the following methods:

Shorten values of the subgroup variable by eliminating redundant characters. For example, if your subgroup variable has values LOT1, LOT2, LOT3, and so on, you can use the SUBSTR function in a DATA step to eliminate "LOT" from each value, and you can modify the horizontal axis label to indicate that the values refer to lots.
Use the TURNHLABELS option to turn the labels vertically.
Use the NPANELPOS= option to force fewer subgroup positions per panel.

If you are using a graphics device, you can also specify a previously defined AXIS statement with the HAXIS= option.

HEIGHT=value

[Graphics]
specifies the height (in vertical screen percent units) of the text for axis labels and legends. This value takes precedence over the HTEXT= value specified in the GOPTIONS statement. This option is recommended for use with software fonts specified with the FONT= option or with the FTEXT= option in the GOPTIONS statement. Related options are LABELHEIGHT= and TESTHEIGHT=.

HMINOR=n

HM=n

[Graphics]
specifies the number of minor tick marks between each major tick mark on the horizontal axis. Minor tick marks are not labeled. The default is 0.

HOFFSET=value

[Graphics]
specifies the length in percent screen units of the offset at both ends of the horizontal axis. You can eliminate the offset by specifying HOFFSET=0.

HREF=values

HREF=SAS-data-set

draws reference lines perpendicular to the horizontal (subgroup) axis on the primary chart. You can use this option in the following ways:

You can specify the values for the lines with an HREF=list. If the subgroup variable is numeric, the values must be numeric. If the subgroup variable is character, the values must be quoted strings of up to 16 characters. If the subgroup variable is formatted, the values must be given as internal values.

Examples of HREF=values follow:
```
   HREF=5
   HREF=5 10 15 20 25 30
   HREF='Shift 1' 'Shift 2' 'Shift 3'
```
You can specify the values for the lines as the values of a variable named _REF_ in an HREF=data set. The type and length of _REF_ must match those of the subgroup variable specified in the chart statement. Optionally, you can provide labels for the lines as values of a variable named _REFLAB_, which must be a character variable of length 16 or less. If you want distinct reference lines to be displayed in charts for different processes specified in the chart statement, you must include a character variable of length 8 or less named _VAR_, whose values are the processes. If you do not include the variable _VAR_, all of the lines are displayed in all of the charts.

Each observation in the HREF=data set corresponds to a reference line. If BY variables are used in the input data set (DATA=, HISTORY=, or TABLE=), the same BY variable structure must be used in the HREF=data set unless you specify the NOBYREF option.

Related options are CHREF=, HREFCHAR=, HREFLABELS=, HREFLABPOS=, LHREF=, and NOBYREF.

HREF2=values

HREF2=SAS-data-set

draws reference lines perpendicular to the horizontal (subgroup) axis on the secondary chart. The conventions for specifying the HREF2= option are identical to those for specifying the HREF=option. Related options are CHREF=, HREFCHAR=, HREF2LABELS=, HREFLABPOS=, LHREF=, and NOBYREF. The HREF2= option is available only in the IRCHART, MRCHART, XRCHART, and XSCHART statements and in the BOXCHART, MCHART, and XCHART statements with the TRENDVAR= option.

HREF2DATA=SAS-data-set

draws reference lines perpendicular to the horizontal (subgroup) axis on the secondary chart. The HREF2DATA= option must be used in place of the HREF2= option to specify a data set using the quoted filename notation.

HREF2LABELS='label1' ... 'labeln'

HREF2LABEL='label1' ... 'labeln'

HREF2LAB='label1' ... 'labeln'

specifies labels for the reference lines requested by the HREF2= option. The number of labels must equal the number of lines. Enclose each label in quotes. Labels can be up to 16 characters. The HREF2LABELS= option is available only in the IRCHART, MRCHART, XRCHART, and XSCHART statements and in the BOXCHART, MCHART, and XCHART statements with the TRENDVAR= option.

HREFCHAR='character'

[Line Printer]
specifies the character used to form the reference lines requested by the HREF=and HREF2= options for a line printer. The default is the vertical bar (|).

HREFDATA=SAS-data-set

draws reference lines perpendicular to the horizontal (subgroup) axis on the primary chart. The HREFDATA= option must be used in place of the HREF=option to specify a data set using the quoted filename notation.

HREFLABELS='label1' ... 'labeln'

HREFLABEL='label1' ... 'labeln'

HREFLAB='label1' ... 'labeln'

specifies labels for the reference lines requested by the HREF=option. The number of labels must equal the number of lines. Enclose each label in quotes. Labels can be up to 16 characters.

HREFLABPOS=n

specifies the vertical position of the HREFLABEL= and HREF2LABEL= labels, as described in the following table. By default, n=2.

1	along top of subplot area
2	staggered from top to bottom of subplot area
3	along bottom of subplot area
4	staggered from bottom to top of subplot area

Figure 46.5 illustrates label positions for values of the HREFLABPOS= option when the VREF= and VREFLABELS= options are as follows:

   HREF=2 4 7
   hreflabels = 'Two' 'Four' 'Seven'

Figure 46.5: Positions for Reference Line Labels

HTML=variable

specifies URLs as values of the specified character variable (or formatted values of a numeric variable). These URLs are associated with points on a control chart when high resolution graphics output is directed into HTML. The value of the HTML= variable should be the same for each observation with a given value of the subgroup variable. See the chapter "Interactive Control Charts" for more information.

HTML_LEGEND=variable

specifies URLs as values of the specified character variable (or formatted values of a numeric variable). These URLs are associated with symbols in the legend for the levels of a symbol-variable. The value of the HTML_LEGEND= variable should be the same for each observation with a given value of symbol-variable.

IDCOLOR=color

[Graphics]
specifies the color of the symbol marker used to identify outliers in schematic box-and-whisker plots produced with the BOXCHART statement when you use one of the following options: BOXSTYLE=SCHEMATIC, BOXSTYLE=SCHEMATICID, and BOXSTYLE=SCHEMATICIDFAR. The default color is the color specified with the CBOXES= option; otherwise, the second color in the device color list is used. The IDCOLOR option is available only in the BOXCHART statement.

IDCTEXT=color

specifies the color for the text used to label outliers or indicate process variable values when you specify one of the keywords SCHEMATICID, SCHEMATICIDFAR, POINTSID, or POINTSJOINID with the BOXSTYLE= option. The default is the color specified with the CTEXT= option.

IDFONT=font

specifies the font for the text used to label outliers or indicate process variable values when you specify one of the keywords SCHEMATICID, SCHEMATICIDFAR, POINTSID, or POINTSJOINID with the BOXSTYLE= option. The default font is SIMPLEX.

IDHEIGHT=value

specifies the height for the text used to label outliers or indicate process variable values when you specify one of the keywords SCHEMATICID, SCHEMATICIDFAR, POINTSID, or POINTSJOINID with the BOXSTYLE= option. The default is the height specified with the HTEXT= option in the GOPTIONS statement.

IDSYMBOL=symbol

[Graphics]
specifies the symbol marker used to identify outliers in schematic box-and-whisker plots produced with the BOXCHART statement when you use one of the following options: BOXSTYLE=SCHEMATIC, BOXSTYLE=SCHEMATICID, and BOXSTYLE=SCHEMATICIDFAR. The default symbol is SQUARE. The IDSYMBOL= option is available only in the BOXCHART statement.

specifies the natural time interval between consecutive subgroup positions when a time, date, or datetime format is associated with a numeric subgroup variable. By default, the INTERVAL= option uses the number of subgroup positions per panel that you specify with the NPANELPOS= option. The default time interval keywords for various time formats are shown in the following table.

Format	Default Keyword	Format	Default Keyword
DATE	DAY	MONYY	MONTH
DATETIME	DTDAY	TIME	SECOND
DDMMYY	DAY	TOD	SECOND
HHMM	HOUR	WEEKDATE	DAY
HOUR	HOUR	WORDDATE	DAY
MMDDYY	DAY	YYMMDD	DAY
MMSS	MINUTE	YYQ	QTR

You can use the INTERVAL= option to modify the effect of the NPANELPOS= option, which specifies the number of subgroup positions per panel (screen or page). The INTERVAL= option enables you to match the scale of the horizontal axis to the scale of the subgroup variable without having to associate a different format with the subgroup variable.

For example, suppose your formatted subgroup values span an overall time interval of 100 days and a DATETIME format is associated with the subgroup variable. Since the default interval for the DATETIME format is DTDAY and since NPANELPOS=50 by default, the chart is displayed with two panels (screens or pages).

Now, suppose your data span an overall time interval of 100 hours and a DATETIME format is associated with the subgroup variable. The chart for these data is created in a single panel, but the data occupy only a small fraction of the chart since the scale of the data (hours) does not match that of the horizontal axis (days). If you specify INTERVAL=HOUR, the horizontal axis is scaled for 50 hours, matching the scale of the data, and the chart is displayed with two panels.

INTSTART=value

specifies the starting value for a numeric horizontal axis. If the value specified is greater than the first subgroup variable value, this option has no effect.

LABELFONT=font

TESTFONT=font

[Graphics]
specifies a software font for labels requested with the ALLLABEL=, ALLLABEL2=, OUTLABEL=, OUTLABEL2=, STARLABEL=, TESTLABEL=, and TESTLABELn= options. Hardware characters are used by default.

LABELHEIGHT=value

TESTHEIGHT=value

[Graphics]
specifies the height (in vertical percent screen units) for labels requested with the ALLLABEL=, ALLLABEL2=, OUTLABEL=, OUTLABEL2=, STARLABEL=, TESTLABEL=, and TESTLABELn= options. The default height is the height specified with the HEIGHT= option or the HTEXT= option in the GOPTIONS statement.

LBOXES=linetype

LBOXES=(variable)

[Graphics]
specifies the line types for the outlines of the box-and-whisker plots created with the BOXCHART statement. You can use one of the following approaches:

You can specify LBOXES=linetype to provide a single linetype for all of the box-and-whisker plots.
You can specify LBOXES=(variable) to provide a distinct line type for each box-and-whisker plot. The variable must be a numeric variable in the input data set, and its values must be valid SAS/GRAPH linetype values (numbers ranging from 1 to 46). The line type for the plot displayed for a particular subgroup is the value of the variable in the observations corresponding to this subgroup. Note that if there are multiple observations per subgroup in the input data set, the values of the variable should be identical for all of the observations in a given subgroup.

The default value is 1, which produces solid lines. The LBOXES= option is available only in the BOXCHART statement.

LCLLABEL='label'

specifies a label for the lower control limit in the primary chart. The label can be of length 16 or less. Enclose the label in quotes. The default label is of the form LCL=value if the control limit has a fixed value; otherwise, the default label is LCL. Related options are LCLLABEL2=, UCLLABEL=, and UCLLABEL2=.

LCLLABEL2='label'

specifies a label for the lower control limit in the secondary chart. The label can be of length 16 or less. Enclose the label in quotes. The default label is of the form LCL=value if the control limit has a fixed value; otherwise, the default label is LCL. The LCLLABEL2= option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements. Related options are LCLLABEL=, UCLLABEL=, and UCLLABEL2=.

LENDGRID=n

[Graphics]
specifies the line type for the grid requested with the ENDGRID option. The default is n=1, which produces a solid line. If you use the LENDGRID= option, you do not need to specify the ENDGRID option.

LGRID=n

[Graphics]
specifies the line type for the grid requested with the GRID option. The default is n=1, which produces a solid line. If you use the LGRID= option, you do not need to specify the GRID option.

LHREF=linetype

LH=linetype

[Graphics]
specifies the line type for reference lines requested with the HREF=and HREF2= options. The default is 2, which produces a dashed line.

LIMITN=n

LIMITN=VARYING

specifies either a fixed or varying nominal sample size for the control limits.

If you specify LIMITN=n, the control limits are computed for the fixed value n, and they do not vary with the subgroup sample sizes. Moreover, subgroup summary statistics are plotted only for those subgroups with a sample size equal to n. You can specify ALLN in conjunction with LIMITN=n to force all of the statistics to be plotted, regardless of subgroup sample size.

If you do not specify LIMITN=n and the subgroup sample sizes are constant, the default value of n is the constant subgroup sample size.

Depending on the chart statement, there are restrictions on the value of n that you can specify with the LIMITN= option. For the MRCHART, RCHART, and XRCHART statements, $2\le n \le 25$ .For the SCHART and XSCHART statements, $n \ge 2$ .For the BOXCHART, MCHART, and XCHART statements, $n \ge 1$ . If you omit the STDDEVIATIONS option for the MCHART or XCHART statements (or use the RANGES option with the BOXCHART statement) n < 26. For the CCHART and UCHART statements, n > 0, and n can assume fractional values (for all other chart statements, n must be a whole number). For the PCHART and NPCHART statements, $n \ge 1$ .

For the IRCHART statement, n has a somewhat different interpretation; it specifies the number of consecutive measurements from which the moving ranges are to be computed, and $n \ge 2$ . You can think of n as a pseudo nominal sample size for the control limits, since the data for an individual measurements and moving range chart are not subgrouped.

Note the difference between the LIMITN= option and the SUBGROUPN= option that is available in the CCHART, NPCHART, PCHART, and UCHART statements. The LIMITN= option specifies a nominal sample size for the control limits, whereas the SUBGROUPN= option provides the sample sizes for the data.

By default, LIMITN=2 in an IRCHART statement. You cannot specify LIMITN= VARYING in an IRCHART statement. For all other chart statements, LIMITN= VARYING is the default.

The following table identifies the chart features that vary when you use LIMITN= VARYING:

Chart
Statement	Features Affected by LIMITN=VARYING
BOXCHART	control limits
CCHART	control limits, central line
MCHART	control limits
MRCHART	control limits on both charts, central line on R chart
NPCHART	control limits, central line
PCHART	control limits
RCHART	control limits, central line
SCHART	control limits, central line
UCHART	control limits
XCHART	control limits
XRCHART	control limits on both charts, central line on R chart
XSCHART	control limits on both charts, central line on s chart

NOTE: As an alternative to specifying the LIMITN= option, you can read the nominal control limit sample size from the variable _LIMITN_ in a LIMITS= data set. See "Input Data Sets" in the chapter for the chart statement in which you are interested.

LIMLABSUBCHAR='character'

specifies a substitution character (such as #) for labels provided as quoted strings with the LCLLABEL=, LCLLABEL2=, UCLLABEL=, UCLLABEL2=, CSYMBOL=, NPSYMBOL=, PSYMBOL=, RSYMBOL=, SSYMBOL=, USYMBOL=, and XSYMBOL= options. For details concerning these options, refer to the "Dictionary of Options" beginning on page 1385 of SAS/QC Software: Usage and Reference. The substitution character must appear in the label. When the label is displayed on the chart, the character is replaced with the value of the corresponding control limit or center line, provided that this value is constant across subgroups. Otherwise, the default label for a varying control limit or center line is displayed.

LLIMITS=linetype

[Graphics]
specifies the line type for control limits. The default is 4, which produces a dashed line.

LSL=value-list

provides lower specification limits used to compute capability indices. If you provide more than one value, the number of values must match the number of processes listed in the chart statement. If you specify only one value, it is used for all the processes.

IMPORTANT: You can use the LSL= option only in conjunction with the OUTLIMITS= option. The SHEWHART procedure uses the specification limits to compute capability indices, and it saves the limits and indices in the OUTLIMITS= data set. For more information, see "Capability Indices" and "Output Data Sets" in the chapter for the chart statement in which you are interested. Also see the entry for the USL= option. The LSL= option is available in the BOXCHART, IRCHART, MCHART, MRCHART, RCHART, SCHART, XCHART, XRCHART, and XSCHART statements.

LSTARCIRCLES=linetypes

[Graphics]
specifies one or more line types for the circles requested with the STARCIRCLES= option. The number of line types should match the number of circles requested, and the line types are paired with the circles in the order specified. The default linetype is 1, which produces a solid line.

Figure 46.6 illustrates circles displayed by the following LSTARCIRCLES= and STARCIRCLES= options:

   starcircles  = 0.0 1.0 0.25 0.5
   lstarcircles = 1 1 2 2

Figure 46.6: Line Types for Reference Circles

LSTARS=linetype

LSTARS=(variable)

[Graphics]
specifies the line types for the outlines of stars requested with the STARVERTICES= option. You can use one of the following approaches:

You can specify LSTARS=linetype to provide a single line type for all of the stars.
You can specify LSTARS=(variable) to provide a distinct line type for each star. The variable must be a numeric variable in the input data set, and its values must be valid SAS/GRAPH line types. The line type for the star positioned at a particular subgroup is the value of the variable in the observations corresponding to this subgroup. Note that if there are multiple observations per subgroup in the input data set, the variable values should be identical for all of the observations in a given subgroup.

See "Displaying Auxiliary Data with Stars" . The default linetype is 1, which produces a solid line.

LTESTS=linetype

LTEST=linetype

[Graphics]
specifies the line type for the line segments that connect patterns of points for which a test for special causes (requested with the TESTS= option) is positive. The default is 1, which produces a solid line.

LTMARGIN=value

LTM=value

[Graphics]
specifies the width (in horizontal percent screen units) of the left marginal area for the plot requested with the LTMPLOT= option. The LTMARGIN= option is avalable only in the IRCHART statement.

LTMPLOT=keyword

[Graphics]
requests a univariate plot of the control chart statistics that is positioned in the left margin of the control chart. The keywords that you can specify and the associated plots are listed in the following table:

*Keyword*	Marginal Plot
HISTOGRAM	histogram
DIGIDOT	digidot plot
SKELETAL	skeletal box-and-whisker plot
SCHEMATIC	schematic box-and-whisker plot
SCHEMATICID	schematic box-and-whisker plot with outliers labeled
SCHEMATICIDFAR	schematic box-and-whisker plot with far outliers labeled

The LTMPLOT= option is available only in the IRCHART statement; see Example 34.3 for an example. Refer to Hunter (1988) for a description of digidot plots, and see the entry for the BOXSTYLE= option for a description of the various box-and-whisker plots. Related options are LTMARGIN=, RTMARGIN=, and RTMPLOT=.

LVREF=linetype

LV=linetype

[Graphics]
specifies the line type for reference lines requested by the VREF= and VREF2= options. The default is 2, which produces a dashed line.

LZONES=n

[Graphics]
specifies the line type for lines that delineate zones A, B, and C for standard tests requested with the TESTS= and/or TESTS2= options. The default is n=2, which produces a dashed line.

MAXPANELS=n

specifies the maximum number of pages or screens for a chart. By default, n=20.

MEDCENTRAL=AVGMEAN | AVGMED | MEDMED

identifies a method for estimating the process mean $\mu$ ,which is represented by the central line on a median chart. The methods corresponding to each keyword are given in the following table:

Keyword	Method for Estimating Process Mean
AVGMEAN	average of subgroup means
AVGMED	average of subgroup medians
MEDMED	median of subgroup medians

The default keyword is AVGMED. The MEDCENTRAL= option is available only in the MCHART and MRCHART statements and in the BOXCHART statement with the CONTROLSTAT=MEDIAN option.

MISSBREAK

determines how subgroups are formed when observations are read from a DATA= data set and a character subgroup-variable is provided. When you specify the MISSBREAK option, observations with missing values of the subgroup variable are not processed. Furthermore, the next observation with a nonmissing value of the subgroup-variable is treated as the beginning observation of a new subgroup even if this value is identical to the most recent nonmissing subgroup value. In other words, by specifying the option MISSBREAK and by inserting an observation with a missing subgroup-variable value into a group of consecutive observations with the same subgroup-variable value, you can split the group into two distinct subgroups of observations.

By default (if MISSBREAK is not specified), observations with missing values of the subgroup variable are not processed, and all remaining observations with the same consecutive value of the subgroup-variable are treated as a single subgroup.

MU0=value

specifies a known (standard) value $\mu_0$ for the process mean $\mu$ . By default, $\mu$ is estimated from the data. The MU0= option is available in the BOXCHART, IRCHART, MCHART, MRCHART, XCHART, XRCHART, and XSCHART statements.

NOTE: As an alternative to specifying MU0= $\mu_0$ , you can read a predetermined value for $\mu_0$ from the variable _MEAN_ in a LIMITS= data set. See "Input Data Sets" in the chapter for the chart statement in which you are interested.

NAME='string'

[Graphics]
specifies a name for the primary chart of length 8 or less that appears in the PROC GREPLAY master menu. The default name is 'SHEWHART'. A related option is DESCRIPTION=.

NAME2='string'

[Graphics]
specifies a name for the secondary chart of length 8 or less that appears in the PROC GREPLAY master menu. The default name is 'SHEWHART'. The NAME2= option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements, and it is used in conjunction with the SEPARATE option. A related option is DESCRIPTION2=.

NDECIMAL=n

specifies the number of decimal digits in the default labels for the control limits and the central line in the primary chart. The default is one more than the maximum number of decimal digits in the vertical axis tick mark labels. For example, if the vertical axis tick mark label with the largest number of digits after the decimal point is 110.05, the default is n=3.

NDECIMAL2=n

specifies the number of decimal digits in the default labels for the control limits and central line in a secondary chart. The default is one more than the maximum number of decimal digits in the vertical axis tick mark labels. The NDECIMAL2= option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements.

NEEDLES

connects plotted points to the central line with vertical line segments (needles). See Example 37.2 for an example. By default, adjacent points are connected to one another. The NEEDLES option is available in all chart statements except the BOXCHART statement.

NMARKERS

identifies a plotted subgroup summary statistic with a special symbol marker (character) when the corresponding subgroup sample size is not equal to the nominal control limit sample size n. Specify the nominal control limit sample size n with the LIMITN= option or with the variable _LIMITN_ read from a LIMITS= data set. The following table summarizes the identification:

Sample Size	Graphics Device Symbol	Line Printer Character
< n	$\bigtriangledown$	L
> n	$\bigtriangleup$	G

A legend that explains the symbols is displayed at the bottom of the chart. This legend can be suppressed with the NOLEGEND option.

The NMARKERS option is not available in the IRCHART statement. The NMARKERS option applies only when specified in conjunction with the ALLN option and a fixed nominal control limit sample size provided with the LIMITN= option or the variable _LIMITN_. See Example 43.3 for an illustration.

NO3SIGMACHECK

suppresses the check for $3\sigma$ limits when tests for special causes are requested. This allows tests for special causes to be applied when the SIGMAS= option is used to specify control limits other than the default $3\sigma$ limits. This option should not be used for standard control chart applications, since the standard tests for special causes assume $3\sigma$ limits.

NOBYREF

specifies that the reference line information in an HREF=, HREF2=, VREF=, or VREF2= data set is to be applied uniformly to charts created for all the BY groups in the input data set (DATA=, HISTORY=, or TABLE=). If you specify the NOBYREF option, you do not need to provide BY variables in the reference line data set. By default, you must provide BY variables.

NOCHART

suppresses the creation of the chart. You typically specify the NOCHART option when you are using the procedure to compute control limits and save them in an output data set. You can also use the NOCHART option when you are tabulating results with the TABLE and related options.

In the IRCHART, MRCHART, XRCHART, and XSCHART statements, the NOCHART option suppresses the creation of both the primary and secondary charts. If you use a graphics device and specify the NOCHART option, the chart is not saved in a graphics catalog. To save the chart in a graphics catalog while suppressing the display of the chart, specify the NODISPLAY option in a GOPTIONS statement.

NOCHART2

suppresses the creation of a secondary chart. You typically use this option in the IRCHART statement to create a chart for individual measurements and suppress the accompanying chart for moving ranges. The NOCHART2 option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements.

NOCONNECT

suppresses line segments that connect points on the chart. By default, points are connected except in box charts produced with the BOXCHART statement (see the BOXCONNECT option).

NOCTL

suppresses the display of the central line in a primary chart.

NOCTL2

suppresses the display of the central line in a secondary chart. The NOCTL2 option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements.

NOFRAME

suppresses the default frame drawn around the chart.

NOHLABEL

suppresses the label for the horizontal (subgroup) axis. Use the NOHLABEL option when the meaning of the axis is evident from the tick mark labels, such as when a date format is associated with the subgroup variable.

NOLCL

suppresses the display of the lower control limit in a primary chart.

NOLCL2

suppresses the drawing of the lower control limit in a secondary chart. The NOLCL2 option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements.

NOLEGEND

suppresses the default legend for subgroup sample sizes, which appears by default below the chart. This option also suppresses the legend displayed by the NMARKERS option. Use the NOLEGEND option when the subgroup sample sizes are constant and equal to the control limit sample size, since the control limit sample size is displayed in the upper right corner of the chart.

NOLIMIT0

suppresses the display of a fixed lower control limit if and only if the value of the limit is zero. This option is useful in situations where a lower limit of zero is considered to be uninformative or visually distracting (for instance, on certain p charts or R charts). The NOLIMIT0 option is available with all chart statements except BOXCHART, MCHART, and XCHART. For the IRCHART, MRCHART, XRCHART, and XSCHART statements, the NOLIMIT0 option applies only to the secondary chart.

NOLIMIT1

suppresses the display of a fixed upper control limit on a p chart if and only if the value of the control limit is 1 (or 100%), or on an np chart if and only if the value of the control limit is n. The NOLIMIT1 option is available only in the NPCHART and PCHART statements.

NOLIMITLABEL

suppresses the default labels for the control limits and central lines.

NOLIMITS

suppresses the display of control limits. This option is particularly useful if you are using the BOXCHART statement to create side by side box-and-whisker plots; in this case, you should also use one of the BOXSTYLE= options.

NOLIMITSFRAME

suppresses the default frame for the control limit information that is displayed across the top of the chart when multiple sets of control limits with distinct multiples of $\sigma$ and nominal control limit sample sizes are read from a LIMITS= data set.

NOLIMITSLEGEND

suppresses the legend for the control limits (for example, 3 $\sigma$ Limits For n=5), which appears by default in the upper right corner of the chart.

NOPHASEFRAME

suppresses the default frame for the legend requested by the PHASELEGEND option.

NOREADLIMITS

specifies that the control limits for each process listed in the chart statement are not to be read from the LIMITS= data set specified in the PROC SHEWHART statement. There are two basic methods of displaying control limits: calculating control limits from the data and reading control limits from a LIMITS= data set. If you want control limits calculated from the data, you can do one of the following:

Do not specify a LIMITS= data set.
If you specify a LIMITS= data set, also specify the NOREADLIMITS option.

Otherwise, if you specify a LIMITS= data set in the PROC SHEWHART statement, the procedure reads control limits from that data set.^*

The following example illustrates the NOREADLIMITS option:

   proc shewhart data=pistons limits=diamlim;
      xrchart diameter*hour;
      xrchart diameter*hour / noreadlimits;
   run;

The first XRCHART statement reads the control limits from the first observation in the data set DIAMLIM for which the variable _VAR_ is equal to diameter and the variable _SUBGRP_ is equal to hour. The second XRCHART statement computes the control limits from the measurements in the data set PISTONS. Note that the second XRCHART statement is equivalent to the following statements, which are more commonly used:

   proc shewhart data=pistons;
      xrchart diameter*hour;
   run;

For more information about reading control limits from a LIMITS= data set, see the entry for the READLIMITS option and "Displaying Multiple Sets of Control Limits" .

NOTCHES

[Graphics]
specifies that box-and-whisker plots created by the BOXCHART statement are to be notched. The endpoints of the notches are located at the median plus and minus $1.58( {IQR} / \sqrt{n})$ , where IQR is the interquartile range and n is the subgroup sample size. The medians (central lines) of two box-and-whisker plots are significantly different at approximately the 0.05 level if the corresponding notches do not overlap. Refer to McGill and others (1978). Figure 46.7 illustrates the NOTCHES option. Notice the folding effect at the bottom, which happens when the endpoint of a notch is beyond its corresponding quartile. This situation occurs typically only when the subgroup sample size is small.

Figure 46.7: NOTCHES Option for Box-and-Whisker Plots

The NOTCHES option is also illustrated in Output 32.3 and is available only in the BOXCHART statement.

NOTICKREP: applies to character-valued subgroup-variables and specifies that only the first occurrence of repeated, adjacent subgroup values is to be labeled on the horizontal axis.
NOTRENDCONNECT: suppresses line segments that connect points on a trend chart. Points are connected by default. The NOTRENDCONNECT option is available only in the BOXCHART, MCHART, and XCHART statements when the TRENDVAR= option is used.
NOTRUNC: overrides the vertical axis truncation at zero, which is applied by default to c charts, moving range charts, np charts, p charts, R charts, s charts, and u charts. This option is useful if you are creating a customized version of one of these charts and want to replace the plotted statistics and control limits with values read from a TABLE= input data set that can be positive or negative. Do not use the NOTRUNC option in standard control chart applications. This option is not available in the BOXCHART, MCHART, and XCHART statements.
NOUCL: suppresses the display of the upper control limit in a primary chart.
NOUCL2: suppresses the display of the upper control limit in a secondary chart. The NOUCL2 option is available in the IRCHART, MRCHART, XRCHART, and XSCHART statements.
NOVANGLE: [Graphics]
requests vertical axis labels that are strung out vertically. By default, the labels are drawn at an angle of 90 degrees if a software font is used.
NPANELPOS=n
NPANEL=n: specifies the number of subgroup positions per panel on each chart. A panel is defined as a screen or page (or a half-screen or half-page if you are also using the BILEVEL option). You typically specify the NPANELPOS= option to display more points on a panel than the default number, which is n=50 for all chart statements except the BOXCHART statement, for which the default is n=20.

You can specify a positive or negative number for n. The absolute value of n must be at least 5. If n is positive, the number of position