The LIFEREG Procedure

PROBPLOT Statement

  • PROBPLOT | PPLOT </options>;

You can use the PROBPLOT statement to create a probability plot from lifetime data. The data can be uncensored, right censored, or arbitrarily censored. You can specify any number of PROBPLOT statements after a MODEL statement. The syntax used for the response in the MODEL statement determines the type of censoring assumed in creating the probability plot. The model fit with the MODEL statement is plotted along with the data. If there are covariates in the model, they are set to constant values specified in the XDATA= data set when creating the probability plot. If no XDATA= data set is specified, continuous variables are set to their overall mean values and categorical variables specified in the CLASS statement are set to their highest levels.

Table 10 summarizes the options available in the PROBPLOT statement.

Table 10: PROBPLOT Statement Options

Option Description
HCL Computes and draws confidence limits for the predicted probabilities
HLOWER= Specifies value as the lower lifetime axis tick mark
HUPPER= Specifies value as the upper lifetime axis tick mark
HREF Draws reference lines perpendicular to the horizontal axis
HREFLABELS= Specifies labels for the lines requested by the HREF= option
ITPRINTEM Displays the iteration history for the Turnbull algorithm
MAXITEM= Specifies the maximum number of iterations for the Turnbull algorithm
NOCENPLOT Suppresses the plotting of censored data points
NOCONF Suppresses the default confidence bands
NODATA Suppresses plotting of the estimated empirical probability plot
NOFIT Suppresses the fitted probability (percentile) line and confidence bands
NOFRAME Suppresses the frame around plotting areas
NOGRID Suppresses grid lines
NOPOLISH Suppresses setting small interval probabilities to zero in the Turnbull algorithm
NPINTERVALS= Displays one of the two kinds of confidence limits
PCTLIST= Specifies the list of percentages for which to compute percentile estimates
PLOWER= Specifies the lower limit on the probability axis scale
PPOS= Specifies the plotting position type
PPOUT Displays a table of the cumulative probabilities
PRINTPROBS Displays intervals and associated probabilities for the Turnbull algorithm
PROBLIST= Specifies the list of initial values for the Turnbull algorithm
PUPPER= Specifies the upper limit on the probability axis scale
ROTATE Requests probability plots with probability scale on the horizontal axis
SQUARE Makes the layout of the probability plots square
TOLLIKE= Specifies the criterion for convergence in the Turnbull algorithm
TOLPROB= Specifies the criterion for setting the interval probability to zero in the Turnbull algorithm
VREF Draws reference lines perpendicular to the vertical axis
VREFLABELS= Specifies labels for the lines requested by the VREF= option


You can specify the following options to control the content, layout, and appearance of a probability plot.

The following options are available if ODS Graphics is enabled.

HCL

computes and draws confidence limits for the predicted probabilities in the horizontal direction.

HLOWER=value

specifies the lower limit on the lifetime axis scale. The HLOWER= option specifies value as the lower lifetime axis tick mark. The tick mark interval and the upper axis limit are determined automatically.

HUPPER=value

specifies value as the upper lifetime axis tick mark. The tick mark interval and the lower axis limit are determined automatically.

HREF <(INTERSECT)> =value-list

requests reference lines perpendicular to the horizontal axis be drawn at horizontal axis values in the value-list. If (INTERSECT) is specified, a second reference line perpendicular to the vertical axis is drawn that intersects the fit line at the same point as the horizontal axis reference line. If a horizontal axis reference line label is specified with the HREFLABELS= option, the intersecting vertical axis reference line is labeled with the vertical axis value. See also the CHREF=, HREFLABELS=, and LHREF= options.

HREFLABELS=’label1’ …’labeln’
HREFLABEL=’label1’ …’labeln’
HREFLAB=’label1’ …’labeln’

specifies labels for the 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.

ITPRINTEM

displays the iteration history for the Turnbull algorithm.

MAXITEM=n1 <,n2>

specifies the maximum number of iterations for the Turnbull algorithm. Iteration history will be displayed in increments of n2 if requested with the ITPRINTEM option. See the section Arbitrarily Censored Data for details.

NOCENPLOT

suppresses the plotting of censored data points.

NOCONF

suppresses the default confidence bands on the probability plot.

NODATA

suppresses plotting of the estimated empirical probability plot.

NOFIT

suppresses the fitted probability (percentile) line and confidence bands.

NOFRAME

suppresses the frame around plotting areas.

NOGRID

suppresses grid lines.

NOPOLISH

suppresses setting small interval probabilities to zero in the Turnbull algorithm.

NPINTERVALS=interval-type

specifies one of the two kinds of confidence limits for the estimated cumulative probabilities, pointwise (NPINTERVALS=POINT) or simultaneous (NPINTERVALS=SIMUL), requested by the PPOUT option to be displayed in the tabular output.

PCTLIST=value-list

specifies the list of percentages for which to compute percentile estimates; value-list must be a list of values separated by blanks or commas. Each value in the list must be between 0 and 100.

PLOWER=value

specifies the lower limit on the probability axis scale. The PLOWER= option specifies value as the lower probability axis tick mark. The tick mark interval and the upper axis limit are determined automatically.

PPOS=plotting-position-type

specifies the plotting position type. See the section Probability Plotting for details.

PPOS= Method
EXPRANK Expected ranks
MEDRANK Median ranks
MEDRANK1 Median ranks (exact formula)
KM Kaplan-Meier
MKM Modified Kaplan-Meier (default)

PPOUT

specifies that a table of the cumulative probabilities plotted on the probability plot be displayed. Kaplan-Meier estimates of the cumulative probabilities are also displayed, along with standard errors and confidence limits. The confidence limits can be pointwise or simultaneous, as specified by the NPINTERVALS= option.

PRINTPROBS

displays intervals and associated probabilities for the Turnbull algorithm.

PROBLIST=value-list

specifies the list of initial values for the Turnbull algorithm.

PUPPER=value

specifies the upper limit on the probability axis scale. The PUPPER= option specifies value as the upper probability axis tick mark. The tick mark interval and the lower axis limit are determined automatically.

ROTATE

requests probability plots with probability scale on the horizontal axis.

SQUARE

makes the layout of the probability plots square.

TOLLIKE=value

specifies the criterion for convergence in the Turnbull algorithm.

TOLPROB=value

specifies the criterion for setting the interval probability to zero in the Turnbull algorithm.

VREF<(INTERSECT)>=value-list

requests reference lines perpendicular to the vertical axis be drawn at vertical axis values in the value-list. If (INTERSECT) is specified, a second reference line perpendicular to the horizontal axis is drawn that intersects the fit line at the same point as the vertical axis reference line. If a vertical axis reference line label is specified with the VREFLABELS= option, the intersecting horizontal axis reference line is labeled with the horizontal axis value. See also the CVREF=, LVREF=, and VREFLABELS= options.

VREFLABELS=’label1’ …’labeln’
VREFLABEL=’label1’ …’labeln’
VREFLAB=’label1’ …’labeln’

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

Last updated: December 09, 2022