PROC LIFEREG: PROBPLOT Statement :: SAS/STAT(R) 9.2 User's Guide, Second Edition

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.

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

Traditional Graphics

The following options are available if you use traditional graphics—that is, if ODS Graphics is not enabled.

ANNOTATE=SAS-data-set

ANNO=SAS-data-set

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.

CAXIS=color

CAXES=color

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.

CCENSOR=color

specifies the color for filling the censor plot area. The default is the first color in the device color list.

CENBIN

plots censored data as frequency counts (rounding for noninteger frequency) rather than as individual points.

CENCOLOR=color

specifies the color for the censor symbol. The default is the first color in the device color list.

CENSYMBOL=symbol | (symbol 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.

CFIT=color

specifies the color for the fitted probability line and confidence curves. The default is the first color in the device color list.

CFRAME=color

CFR=color

specifies the color for the area enclosed by the axes and frame. This area is not shaded by default.

CGRID=color

specifies the color for grid lines. The default is the first color in the device color list.

CHREF=color

CH=color

specifies the color for lines requested by the HREF= option. The default is the first color in the device color list.

CTEXT=color

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.

CVREF=color

CV=color

specifies the color for lines requested by the VREF= option. The default is the first color in the device color list.

DESCRIPTION=’string’

DES=’string’

specifies a description, up to 40 characters, that appears in the PROC GREPLAY master menu. The default is the variable name.

FONT=font

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.

HCL

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

HEIGHT=value

specifies the height of text used outside framed areas. The default value is 3.846 (in percentage).

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.

HOFFSET=value

specifies the offset for the horizontal axis. The default value is 1.

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. 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, 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.

HREFLABPOS= $\text{[math]}$

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

INBORDER

requests a border around probability plots.

INTERTILE=value

specifies the distance between tiles.

ITPRINTEM

displays the iteration history for the Turnbull algorithm.

JITTER=value

specifies the amount to jitter overlaying plot symbols, in units of symbol width.

LFIT=linetype

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).

LGRID=linetype

specifies a line style for all grid lines; linetype is between 1 and 46. The default is 35.

LHREF=linetype

LH=linetype

specifies the line type for lines requested by the HREF= option. The default is 2, which produces a dashed line.

LVREF=linetype

LV=linetype

specifies the line type for lines requested by the VREF= option. The default is 2, which produces a dashed line.

MAXITEM=n1 <,n2> n1

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.

NAME=’string’

specifies a name for the plot, up to eight characters, that appears in the PROC GREPLAY master menu. The default is ’LIFEREG’.

NOCENPLOT

suppresses the plotting of censored data points.

NOCONF

suppresses the default percentile 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.

NOHLABEL

suppresses horizontal labels.

NOHTICK

suppresses horizontal tick marks.

NOPOLISH

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

NOVLABEL

suppresses vertical labels.

NOVTICK

suppresses vertical tick marks.

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.

PRINTPROBS

displays intervals and associated probabilities 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.

PPOS=character-list

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.

PROBLIST=value-list

specifies the list of initial values for the Turnbull algorithm.

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.

VAXISLABEL=‘string’

specifies a label for the vertical axis.

VREF=value-list

requests reference lines perpendicular to the vertical axis. 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, the intersecting horizontal axis reference line is labeled with the horizontal axis value. See also the entries for 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.

VREFLABPOS= $\text{[math]}$

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

WAXIS= $\text{[math]}$

specifies line thickness for axes and frame. The default value is 1.

WFIT= $\text{[math]}$

specifies line thickness for fitted curves. The default value is 1.

WGRID= $\text{[math]}$

specifies line thickness for grids. The default value is 1.

WREFL= $\text{[math]}$

specifies line thickness for reference lines. The default value is 1.

ODS Graphics

The following options are available if ODS Graphics is enabled.