PROBPLOT Statement |
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.
You can specify the following options to control the content, layout, and appearance of a probability plot.
The following options are available if you use traditional graphics—that is, if ODS Graphics is not enabled.
specifies an Annotate data set, as described in SAS/GRAPH Software: Reference, that enables you to add features to the probability plot. The data set you specify with the ANNOTATE= option in the PROBPLOT statement provides the Annotate data set for all plots created by the statement.
specifies the color used 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.
specifies the color for filling the censor plot area. The default is the first color in the device color list.
plots censored data as frequency counts (rounding for noninteger frequency) rather than as individual points.
specifies the color for the censor symbol. The default is the first color in the device color list.
specifies symbols for censored values. The symbol is one of the symbol names (plus, star, square, diamond, triangle, hash, paw, point, dot, and circle) or a letter (A–Z). If you do not specify the CENSYMBOL= option, the symbol used for censored values is the same as for failures.
specifies the color for the fitted probability line and confidence curves. The default is the first color in the device color list.
specifies the color for the area enclosed by the axes and frame. This area is not shaded by default.
specifies the color for grid lines. The default is the first color in the device color list.
specifies the color for lines requested by the HREF= option. The default is the first color in the device color list.
specifies the color for tick mark values and axis labels. The default is the color specified for the CTEXT= option in the most recent GOPTIONS statement.
specifies the color for lines requested by the VREF= option. The default is the first color in the device color list.
specifies a description, up to 40 characters, that appears in the PROC GREPLAY master menu. The default is the variable name.
specifies a software font for reference line and axis labels. You can also specify fonts for axis labels in an AXIS statement. The FONT= font takes precedence over the FTEXT= font specified in the most recent GOPTIONS statement. Hardware characters are used by default.
computes and draws confidence limits for the predicted probabilities based on distribution percentiles instead of the default CDF limits. See the section Confidence Limits for Percentiles for details of the computation.
specifies the height of text used outside framed areas. The default value is 3.846 (in percentage).
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.
specifies the offset for the horizontal axis. The default value is 1.
specifies value as the upper lifetime axis tick mark. The tick mark interval and the lower axis limit are determined automatically.
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.
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.
specifies the vertical position of labels for HREF= lines. The following table shows the valid values for n and the corresponding label placements.
n |
Label Placement |
1 |
Top |
2 |
Staggered from top |
3 |
Bottom |
4 |
Staggered from bottom |
5 |
Alternating from top |
6 |
Alternating from bottom |
specifies the amount to jitter overlaying plot symbols, in units of symbol width.
specifies a line style for fitted curves and confidence limits. By default, fitted curves are drawn by connecting solid lines (linetype = 1), and confidence limits are drawn by connecting dashed lines (linetype = 3).
specifies a line style for all grid lines; linetype is between 1 and 46. The default is 35.
specifies the line type for lines requested by the HREF= option. The default is 2, which produces a dashed line.
specifies the line type for lines requested by the VREF= option. The default is 2, which produces a dashed line.
specifies the maximum number of iterations allowed 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.
specifies a name for the plot, up to eight characters, that appears in the PROC GREPLAY master menu. The default is ’LIFEREG’.
suppresses the default confidence bands on the probability plot.
suppresses plotting of the estimated empirical probability plot.
suppresses the fitted probability (percentile) line and confidence bands.
suppresses setting small interval probabilities to zero in the Turnbull algorithm.
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.
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.
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.
displays intervals and associated probabilities for the Turnbull algorithm.
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.
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) |
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.
specifies the list of initial values for the Turnbull algorithm.
requests probability plots with probability scale on the horizontal axis.
specifies the criterion for convergence in the Turnbull algorithm.
specifies the criterion for setting the interval probability to zero in the Turnbull algorithm.
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.
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.
specifies the horizontal position of labels for VREF= lines. The valid values for n and the corresponding label placements are shown in the following table.
n |
Label Placement |
1 |
Left |
2 |
Right |
specifies line thickness for axes and frame. The default value is 1.
specifies line thickness for fitted curves. The default value is 1.
specifies line thickness for reference lines. The default value is 1.
The following options are available if ODS Graphics is enabled.
computes and draws confidence limits for the predicted probabilities in the horizontal direction.
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.
specifies value as the upper lifetime axis tick mark. The tick mark interval and the lower axis limit are determined automatically.
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.
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.
specifies the maximum number of iterations allowed 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.
suppresses the default confidence bands on the probability plot.
suppresses plotting of the estimated empirical probability plot.
suppresses the fitted probability (percentile) line and confidence bands.
suppresses setting small interval probabilities to zero in the Turnbull algorithm.
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.
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.
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.
displays intervals and associated probabilities for the Turnbull algorithm.
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.
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) |
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.
specifies the list of initial values for the Turnbull algorithm.
requests probability plots with probability scale on the horizontal axis.
specifies the criterion for convergence in the Turnbull algorithm.
specifies the criterion for setting the interval probability to zero in the Turnbull algorithm.
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.
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.