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The LIFETEST Procedure |

**PROC LIFETEST***< options >***;**

Task |
Options |
Description |

Specify Data Set | DATA= | specifies the input SAS data set |

OUTSURV= | names an output data set to contain survival estimates and confidence limits | |

OUTTEST= | names an output data set to contain rank test statistics for association of survival time with covariates limits | |

Specify Model | ALPHA= | sets confidence level for survival estimates |

ALPHAQT= | sets confidence level for survival time quartiles | |

INTERVALS= | specifies interval endpoints for life table calculations | |

MAXTIME= | sets maximum value of time variable for plot | |

METHOD= | specifies method to compute survivor function | |

MISSING | allows missing values to be a stratum level | |

NINTERVAL= | specifies number of intervals for life table estimates | |

SINGULAR= | sets tolerance for testing singularity of covariance matrix of rank statistics | |

TIMELIM= | specifies the time limit used to estimate the mean survival time and its standard error | |

WIDTH= | specifies width of intervals for life table estimates | |

Control Output | CENSOREDSYMBOL= | defines symbol used for censored observations in plots |

EVENTSYMBOL= | specifies symbol used for event observations in plots | |

FORMCHAR(1,2,7,9)= | defines characters used for line printer plot axes | |

LINEPRINTER | specifies that plots are produced by line printer | |

NOCENSPLOT | suppresses the plot of censored observations | |

NOPRINT | suppresses display of output | |

NOTABLE | suppresses display of survival function estimates | |

PLOTS= | plots survival estimates | |

REDUCEOUT | specifies that only INTERVAL= or TIMELIST= observations are listed in the OUTSURV= data set | |

TIMELIST= | specifies a list of time points at which the Kaplan-Meier estimates are displayed | |

Enhance Graphical Output | ANNOTATE= | specifies an annotate data set that adds features to plots |

DESCRIPTION= | specifies string that appears in the description field of the PROC GREPLAY master menu for the plots | |

GOUT= | specifies graphics catalog name for saving graphics output | |

LANNOTATE= | specifies an input data set that contains variables for local annotation |

**ALPHA=***value*-
specifies a number between 0.0001 and 0.9999 that
sets the confidence level for the confidence
intervals for the survivor function.
The confidence level for the interval is 1 - ALPHA.
For example, the option ALPHA=0.05 requests a 95% confidence
interval for the SDF at each time point. The
default value is 0.05.
**ALPHAQT=***value*-
specifies a number between 0.0001 and 0.9999 that
sets the level for the confidence
intervals for the quartiles of the survival time.
The confidence level for the interval is 1 - ALPHAQT.
For example, the option ALPHAQT=0.05 requests a 95% confidence
interval for the quantiles of the survival time. The default value is 0.05.
**ANNOTATE=***SAS-data-set***ANNO=***SAS-data-set*-
specifies an input data set that contains appropriate
variables for annotation. The ANNOTATE= option enables you
to add features (for example, labels explaining extreme
observations) to plots produced on graphics devices.
The ANNOTATE= option cannot be used if the
LINEPRINTER option is specified.
The data set specified
must be an ANNOTATE= type data set, as described in
*SAS/GRAPH Software: Reference*.

The data set specified with the ANNOTATE= option in the PROC LIFETEST statement is "global" in the sense that the information in this data set is displayed on every plot produced by a single invocation of PROC LIFETEST. **CENSOREDSYMBOL=***name*|*'string'***CS=***name*|*'string'*-
specifies the symbol value for the censored observations.
The value,
*name*or*'string'*, is the symbol value specification allowed in SAS/GRAPH software. The default is CS=CIRCLE. If you want to omit plotting the censored observations, specify CS=NONE. The CENSOREDSYMBOL= option cannot be used if the LINEPRINTER option is specified. **DATA=***SAS-data-set*-
names the SAS data set used by PROC LIFETEST.
By default, the most recently created SAS data set is used.
**DESCRIPTION='***string*'**DES='***string*'-
specifies a descriptive string of up to 40 characters
that appears in the "Description" field of the
graphics catalog. The description does not appear on the
plots. By default, PROC LIFETEST assigns a description
of the form PLOT OF
*vname*vs*hname*, where*vname*and*hname*are the names of the*y*variable and the*x*variable, respectively. The DESCRIPTION= option cannot be used if the LINEPRINTER option is specified. **EVENTSYMBOL=***name*|*'string'***ES=***name*|*'string'*-
specifies the symbol value for the event observations.
The value,
*name*or*'string'*, is the symbol value specification allowed in SAS/GRAPH software. The default is ES=NONE. The EVENTSYMBOL= option cannot be used if the LINEPRINTER option is specified. **FORMCHAR(1,2,7,9)=***'string'*-
defines the characters used for constructing
the vertical and horizontal axes of the line printer plots.
The string should be four characters.
The first and second characters define the vertical and
horizontal bars, respectively, which are also used in drawing
the
*steps*of the product-limit survival function. The third character defines the tick mark for the axes, and the fourth character defines the lower left corner of the plot. If the FORMCHAR option in PROC LIFETEST is not specified, the value supplied, if any, with the system option FORMCHAR= is used. The default is FORMCHAR(1,2,7,9)='|-+-'. Any character or hexadecimal string can be used to customize the plot appearance. To send the plot output to a printer with the IBM graphics character set (1 or 2) or display it directly on your PC screen, you can use the following hexadecimal representationformchar(1,2,7,9)='B3C4C5C0'x

or system optionformchar='B3C4DAC2BFC3C5B4C0C1D9'x

Refer to the chapter titled "The PLOT Procedure," in the*SAS Procedures Guide*or the section "System Options" in*SAS Language Reference: Dictionary*for further information. **GOUT=***graphics-catalog*-
specifies the graphics catalog for saving graphics output
from PROC LIFETEST. The default is WORK.GSEG.
The GOUT= option cannot be used if the
LINEPRINTER option is specified.
For more information, refer to the chapter titled "The GREPLAY
Procedure" in
*SAS/GRAPH Software: Reference*. **INTERVALS=***values*-
specifies a list of interval endpoints for the life table calculations.
These endpoints must all be nonnegative numbers.
The initial interval is assumed to start at zero
whether or not zero is specified in the list.
Each interval contains its lower endpoint but does not contain its
upper endpoint.
When this option is used with the product-limit method,
it reduces the number of survival estimates displayed
by displaying only the estimates for the smallest
time within each specified interval.
The INTERVALS= option can be specified
in any of the following ways:
list separated by blanks `intervals=1 3 5 7`

list separated by commas `intervals=1,3,5,7`

x to y `intervals=1 to 7`

x to y by z `intervals=1 to 7 by 1`

combination of the above `intervals=1,3 to 5,7`

For example, the specificationintervals=5,10 to 30 by 10

produces the set of intervals **LANNOTATE=***SAS-data-set***LANN=***SAS-data-set*-
specifies an input data set that contains variables for
local annotation. You can use the LANNOTATE= option to
specify a different annotation for each BY group, in which
case the BY variables must be included in the LANNOTATE=
data set.
The LANNOTATE= option cannot be used if the
LINEPRINTER option is specified.
The data set specified must be
an ANNOTATE= type data set, as described in
*SAS/GRAPH Software: Reference*.

If there is no BY-group processing, the ANNOTATE= and LANNOTATE= options have the same effects. **LINEPRINTER****LS**-
specifies that plots are produced by a line printer instead of by a
graphical device.
**MAXTIME=***value*-
specifies the maximum value of the time variable allowed
on the plots so that outlying points do not
determine the scale of the time axis of the plots.
This parameter only affects the displayed
plots and has no effect on the calculations.
**METHOD=***type*-
specifies the method used to compute
the survival function estimates.
Valid values for
*type*are as follows.- PL | KM
- specifies that product-limit (PL)
or Kaplan-Meier (KM) estimates are computed.
- ACT | LIFE | LT
- specifies that life table (or actuarial) estimates are computed.

By default, METHOD=PL. **MISSING**-
allows missing values for numeric variables and blank
values for character variables as valid stratum levels.
See the section "Missing Values" for details.

By default, PROC LIFETEST does not use observations with missing values for any stratum variables. **NINTERVAL=***value*-
specifies the number of intervals used to compute the
life table estimates of the survivor function.
This parameter is overridden by the
WIDTH= option or the INTERVALS= option.
When you specify the NINTERVAL= option, PROC LIFETEST tries to find an
interval that results in round numbers for the endpoints.
Consequently, the number of intervals may
be different from the number requested.
Use the INTERVALS= option to
control the interval endpoints.
The default is NINTERVAL=10.
**NOCENSPLOT****NOCENS**-
requests that the plot of censored observations
be suppressed when the PLOTS= option is specified.
This option is not needed when the life table method
is used to compute the survival estimates, since
the plot of censored observations is not produced.
**NOPRINT**- suppresses the display of output. This option is useful when only an output data set is needed. Note that this option temporarily disables the Output Delivery System (ODS). For more information, see Chapter 15, "Using the Output Delivery System."
**NOTABLE**-
suppresses the display of survival function estimates.
Only the number of censored and event times,
plots, and test results are displayed.
**OUTSURV=***SAS-data-set***OUTS=***SAS-data-set*-
creates an output SAS data set to contain
the estimates of the survival function and
corresponding confidence limits for all strata.
See the section "Output Data Sets"
for more information
on the contents of the OUTSURV= SAS data set.
**OUTTEST=***SAS-data-set***OUTT=***SAS-data-set*-
creates an output SAS data set to contain the overall
chi-square test statistic for association with failure
time for the variables in the TEST statement, the
values of the univariate rank test statistics for
each variable in the TEST statement, and the estimated
covariance matrix of the univariate rank test statistics.
See the section "Output Data Sets"
for more information
on the contents of the OUTTEST= SAS data set.
**PLOTS=***( type <(NAME=name)> <, ..., type <(NAME=name)> > )*-
creates plots of survival estimates or censored observations, where
*type*is the type of plot and*name*is a catalog entry name of up to eight characters. Valid values of*type*are as follows:- CENSORED | C
- specifies a plot of censored observations by strata.
- SURVIVAL | S
- specifies a plot of the estimated SDF versus time.
- LOGSURV | LS
- specifies a plot of the -log( estimated SDF) versus time.
- LOGLOGS | LLS
- specifies a plot of the log(-log( estimated SDF)
versus log( time).
- HAZARD | H
- specifies a plot of the estimated hazard function versus time.
- PDF | P
- specifies a plot of the estimated probability density function versus time.

Parentheses are required in specifying the plots. For example,plots = (s)

requests a plot of the estimated survivor function versus time, andplots = (s(name=Surv2), h(name=Haz2))

requests a plot of the estimated survivor function versus time and a plot of the estimated hazard function versus time, with Surv2 and Haz2 as their catalog names, respectively. **REDUCEOUT**-
specifies that the OUTSURV= data set contains only those observations
that are included in the INTERVALS= or TIMELIST= option. This
option has no effect if the OUTSURV= option is not specified. It
also has no effect if neither the INTERVALS= option nor the TIMELIST=
option is specified.
**SINGULAR=***value*-
specifies the tolerance for testing singularity of the
covariance matrix for the rank test statistics.
The test requires that a pivot for sweeping a covariance
matrix be at least this number times a norm of the matrix.
The default value is 1E-12.
**TIMELIM=***time-limit*-
specifies the time limit used in the estimation of the mean
survival time and its standard error. The mean survival time can
be shown to be the area under the Kaplan-Meier survival curve.
However, if the largest observed time in the data is censored,
the area under the survival curve is not a closed area. In
such a situation, you
can choose a time limit
*L*and estimate the mean survival curve limited to a time*L*(Lee 1992, pp. 72-76). This option is ignored if the largest observed time is an event time. Valid*time-limit*values are as follows.- EVENT | LET
- specifies that the time limit
*L*is the largest event time in the data. TIMELIM=EVENT is the default. - OBSERVED | LOT
- specifies that the time limit
*L*is the largest observed time in the data. *number*- specifies that the time limit
*L*is the given*number*. The*number*must be positive and at least as large as the largest event time in the data.

**TIMELIST=***number-list*-
specifies a list of time points at which the Kaplan-Meier estimates
are displayed. The time points are listed in the column labeled as
_TIME_. Since the Kaplan-Meier survival curve is a decreasing
step function, each given time point falls in an interval that
has a constant survival estimate. The event time that corresponds
to the beginning of the time interval is displayed along with its
survival estimate.
**WIDTH=***value*-
sets the width of the intervals used in the
life table calculation of the survival function.
This parameter is overridden by the INTERVALS= option.

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