The basic syntax for the NPCHART statement is as follows:
- NPCHART process*subgroup-variable ;
The general form of this syntax is as follows:
- NPCHART (processes)*subgroup-variable
<(block-variables ) >
- < =symbol-variable | ='character' >
< / options >;
You can use any number of NPCHART statements in the SHEWHART procedure.
The components of the NPCHART statement are described as follows.
identify one or more processes to be analyzed.
The specification of process depends on
the input data set specified in the PROC SHEWHART statement.
- If numbers of nonconforming items are read from a DATA= data set,
process must be the name of the variable containing
For an example, see "Creating np Charts from Count Data" .
- If proportions of nonconforming items
are read from a HISTORY= data set,
process must be the common prefix of the
summary variables in the HISTORY= data set.
For an example, see "Creating np Charts from Summary Data" .
- If numbers of nonconforming items and control
limits are read
from a TABLE= data set, process must be the value of the
variable _VAR_ in the TABLE= data set.
For an example, see "Saving Control Limits" .
A process is required. If you specify more than one process,
enclose the list in parentheses. For example, the following
statements request distinct np charts for REJECTS and REWORKS:
proc shewhart data=measures;
npchart (rejects reworks)*sample / subgroupn=100;
Note that when data are read from a DATA= data set,
the SUBGROUPN= option, which specifies subgroup sample sizes,
is the variable that identifies subgroups in the data. The
subgroup-variable is required. In the preceding NPCHART
statement, SAMPLE is the subgroup variable.
For details, see "Subgroup Variables" .
are optional variables that group the data into blocks of
consecutive subgroups. The blocks are labeled in a legend, and each
block-variable provides one level of labels in the legend.
See "Displaying Stratification in Blocks of Observations" for an example.
is an optional variable whose levels (unique values)
determine the symbol marker or character used to plot numbers of
- If you produce a chart on a line printer, an `A' is displayed
for the points corresponding to the first level of the
symbol-variable, a `B' is displayed for the points
corresponding to the second level, and so on.
- If you produce a chart on a graphics device, distinct symbol
markers are displayed for points corresponding to the various
levels of the symbol-variable. You can specify the
symbol markers with SYMBOLn statements.
See "Displaying Stratification in Levels of a Classification Variable" for an example.
specifies a plotting character for charts produced on line printers.
For example, the following statements create an np
chart using an asterisk (*) to plot the points:
proc shewhart data=values;
npchart rejects*day='*' / subgroupn=100;
- enhance the appearance of the chart, request additional analyses,
save results in data sets, and so on. The "Summary of
Options" section, which follows, lists all options by function.
Chapter 46, "Dictionary of Options," describes each
option in detail.
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.