<label:>PROBPLOT
variable <
censor-variable(values)> <=group-variables> </ options> ;
<label:>PROBPLOT
(variable1 variable2) <=group-variables> </ options> ;
You use the PROBPLOT statement to create a probability plot from complete, left-censored, right-censored, or interval-censored data.
You can specify the keyword PPLOT as an alias for PROBPLOT. You can specify any number of PROBPLOT statements after a PROC RELIABILITY statement. Each PROBPLOT statement creates a probability plot and an associated analysis. The probability distribution used in creating the probability plot and performing the analysis is determined by the DISTRIBUTION statement. You can specify an optional label to distinguish between multiple PROBPLOT statements in the output.
See the section Analysis of Right-Censored Data from a Single Population and the section Weibull Analysis Comparing Groups of Data for examples that create probability plots with the PROBPLOT statement.
To create a probability plot, you must specify one variable. If your data are right censored, you must specify a censor-variable and, in parentheses, the values of the censor-variable that correspond to censored data values.
You can optionally specify one or two group-variables (also referred to as classification variables). The PROBPLOT statement displays a probability plot for each level of the group-variables. The observations in a given level are called a cell.
The elements of the PROBPLOT statement are described as follows.
Table 16.35 lists analysis options that are available when you use either traditional graphics or ODS Graphics.
Table 16.35: Analysis Options
Option |
Option Description |
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CONFIDENCE=number |
Specifies the confidence coefficient for all confidence intervals. The number must be between 0 and 1. The default value is 0.95 |
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CONVERGE=number |
Specifies the convergence criterion for maximum likelihood fit. See the section Maximum Likelihood Estimation for details. |
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CONVH=number |
Specifies the convergence criterion for the relative Hessian convergence criterion. See the section Maximum Likelihood Estimation for details. |
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CORRB |
Requests the parameter correlation matrix. |
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COVB |
Requests the parameter covariance matrix. |
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FITTYPE | FIT= fit-specification |
Specifies the method of estimating distribution parameters. The available fit-specifications and their meanings are shown in the following table. |
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|
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INEST | IN=SAS-data-set |
Specifies a SAS data set that can contain initial values, equality constraints, upper bounds, or lower bounds for the scale, shape, and threshold parameters in a three-parameter Weibull model for lifetime data, and applies only to three-parameter Weibull models. See the section INEST Data Set for the Three-Parameter Weibull for details. |
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ITPRINT |
Requests the iteration history for maximum likelihood fit. |
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ITPRINTEM |
Requests the iteration history for the Turnbull algorithm. |
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LRCL |
Requests likelihood ratio confidence intervals for distribution parameters. |
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LRCLPER |
Requests likelihood ratio confidence intervals for distribution percentiles. |
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Requests likelihood ratio confidence intervals for survival and cumulative distribution functions at times specified with the SURVTIME=number-list option. |
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LOCATION=number <LINIT> |
Specifies a fixed or initial value of location parameter. |
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MAKEHAM=number <MKINIT> |
Specifies the fixed or initial value of the Makeham parameter for the three-parameter Gompertz distribution. |
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MAXIT=number |
Specifies the maximum number of iterations allowed for a maximum likelihood fit. |
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MAXITEM=number1 <,number2> |
number1 Specifies the maximum number of iterations allowed for the Turnbull algorithm. Iteration history will be printed in increments of number2 if an iteration history is requested with ITPRINTEM. See the section Interval-Censored Data for details. |
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NOPCTILES |
Suppresses computation of percentiles for standard list of percentage points. |
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NOPOLISH |
Suppresses the setting of small interval probabilities to 0 in the Turnbull algorithm. See the section Interval-Censored Data for details. |
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NPINTERVALS=interval-type |
Specifies the type of nonparametric confidence interval displayed in a probability plot. The available types of intervals are listed in the following table. |
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|
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PCTLIST=number-list |
Specifies a list of percentages for which to compute percentile estimates. The number-list must be a list of numbers separated by blanks or commas. Each number in the list must be between 0 and 100. If this option is not specified, percentiles are computed for a standard list of percentages. |
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Specifies the type of parametric pointwise confidence interval displayed in a probability plot. The available types of intervals are listed in the following table. The default type is PROBABILITY, pointwise confidence intervals on cumulative failure probability. |
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|
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PPOS=plotting-position |
Specifies the plotting-position type used to compute nonparametric estimates of the probability distribution function. See the section Probability Plotting for details. The plotting position types available are shown in the following table. |
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|
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PPOUT |
Requests a table of nonparametric cumulative probabilities in the printed output. |
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PRINTPROBS |
Specifies that intervals and associated probabilities for the Turnbull algorithm be printed. |
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PROBLIST=number-list |
Specifies a list of initial values for Turnbull algorithm. See the section Interval-Censored Data for details. |
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PSTABLE=number |
Specifies a stable parameterization. The number must be between 0 and 1. See the section Stable Parameters for further information. |
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READOUT |
Specifies the data have the readout structure. |
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SCALE=number <SCINIT> |
Specifies a fixed or initial value of the scale parameter. |
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SHAPE=number <SHINIT> |
Specifies a fixed or initial value of the shape parameter. |
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SINGULAR=number |
Specifies the singularity criterion for matrix inversion. |
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Requests that the survival function, cumulative distribution function, and confidence limits be computed for values in number-list. See the section Reliability Function for details. |
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THRESHOLD=number |
Specifies a fixed threshold parameter. See Table 16.57 for the distributions with a threshold parameter. |
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TOLLIKE=number |
Specifies the criterion for convergence in the Turnbull algorithm. The default is . See the section Interval-Censored Data for details. |
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TOLPROB=number |
Specifies the criterion for setting interval probabilities to 0 in the Turnbull algorithm. The default is . See the section Interval-Censored Data for details. |
Table 16.36 lists analysis options that are available when ODS Graphics is enabled.
Table 16.36: Analysis Options for ODS Graphics
Option |
Option Description |
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---|---|---|---|---|---|---|---|---|---|
Requests a profile log-likelihood plot of the threshold parameter for a three-parameter Weibull distribution. The options listed in the following table are available; they are specified by enclosing them in parentheses after the PROFILE option. |
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|
Table 16.37 lists plot layout options that are available when you use traditional graphics.
Table 16.37: Probability Plot Layout Options for Traditional Graphics
Option |
Option Description |
---|---|
CENBIN |
Specifies that censored data be plotted as frequency counts rather than as individual points. |
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, circle) or a letter (A–Z). For overlaid plots for groups of data, you can specify different symbols for the groups with a list of symbols or letters, separated by blanks, enclosed in parentheses. If no CENSYMBOL option is specified, the symbol used for censored values is the same as the symbol used for failures. |
HOFFSET=value |
Specifies the offset for the horizontal axis. |
INBORDER |
Requests a border around probability plots. |
INTERTILE=value |
Specifies the distance between tiles. |
LFIT=linetype | (linetype list)) |
Specifies line styles for fit lines and confidence curves in a probability plot. The linetype list is a list of numbers from 1 to 46 representing different linetypes; they can be separated by blanks or commas or can be a list in the form to <by >. |
MISSING1 |
Requests that missing values of the first GROUP= variable be treated as a level of the variable. |
MISSING2 |
Requests that missing values of the second GROUP= variable be treated as a level of the variable. |
NCOLS=n |
Specifies that n columns be plotted on a page. |
NOCENPLOT |
Suppresses the plotting of censored data points. |
NOCONF |
Suppresses the plotting of percentile confidence curves. |
NOFIT |
Suppresses the plotting of fit line and percentile confidence curves. |
NOFRAME |
Suppresses the frame around the plotting area. |
NOINSET |
Suppresses the inset. |
NOPPLEGEND |
Suppresses the legend for overlaid probability plots |
NOPPOS |
Suppresses plotting of symbols for failures in a probability plot. |
NROWS=n |
Specifies that n rows be plotted on a page. |
ORDER1=DATA | FORMATTED | |
Specifies display order for values of the first GROUP= variable. |
ORDER2=DATA | FORMATTED | |
Specifies the display order for values of the second GROUP= variable. |
OVERLAY |
Requests overlaid plots for group variables. |
PCONFPLT |
Plots confidence intervals on probabilities for readout data. |
PPLEGEND = legend-statement-name |
|
| NONE |
Identifies LEGENDn statement to specify a legend for overlaid probability plots. |
PPOSSYMBOL=symbol | (symbol-list) |
Specifies symbols to represent failures on a probability plot. |
ROTATE |
Requests probability plots with the probability scale on the horizontal axis. |
SHOWMULTIPLES |
Requests that the count be displayed for multiple overlaying symbols. |
TURNVLABELS |
Vertically strings out characters in labels for the vertical axis. |
VOFFSET=value |
Specifies value as the length of the offset at the upper end of the vertical axis. |
WFIT=n |
Specifies the line width for the fit line and confidence curves. |
Table 16.38 lists plot layout options that are available when you use ODS graphics.
Table 16.38: Probability Plot Layout Options for ODS Graphics
Option |
Option Description |
---|---|
MISSING1 |
Requests that missing values of first GROUP= variable be treated as a level of the variable. |
MISSING2 |
Requests that missing values of second GROUP= variable be treated as a level of the variable. |
NCOLS=n |
Specifies that n columns be plotted on a page. |
NOCENPLOT |
Suppresses plotting of censored data points. |
NOCONF |
Suppresses plotting of percentile confidence curves. |
NOFIT |
Suppresses plotting of the fit line and percentile confidence curves. |
NOINSET |
Suppresses the inset. |
NOPPLEGEND |
Suppresses the legend for overlaid probability plots. |
NOPPOS |
Suppresses plotting of symbols for failures in a probability plot. |
NROWS=n |
Specifies that n rows be plotted on a page. |
ORDER1=DATA | FORMATTED | |
|
FREQ | INTERNAL |
Specifies the display order for values of the first GROUP= variable. |
ORDER2=DATA | FORMATTED | |
|
FREQ | INTERNAL |
Specifies the display order for values of the second GROUP= variable. |
OVERLAY |
Requests overlaid plots for group variables. |
PCONFPLT |
Plots confidence intervals on probabilities for readout data. |
ROTATE |
Requests probability plots with the probability scale on the horizontal axis. |
Table 16.39 lists reference line options that are available when you use traditional graphics.
Table 16.39: Reference Line Options for Traditional Graphics
Option |
Option Description |
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---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
HREF <(INTERSECT)>=value-list |
Requests reference lines perpendicular to 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. |
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HREFLABELS=(’label1’ …’labeln’) |
Specifies labels for HREF= lines. |
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HREFLABPOS=n |
Specifies vertical position of labels for HREF= lines. The valid values for n and the corresponding label placements are shown in the following table:
|
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LHREF=linetype |
Specifies the line style for HREF= lines. |
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LVREF=linetype |
Specifies the line style for VREF= lines. |
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VREF <(INTERSECT)>=value-list |
Specifies reference lines perpendicular to 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. |
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VREFLABELS=(’label1’ …’labeln’) |
Specifies labels for VREF= lines. |
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VREFLABPOS=n |
Specifies horizontal position of labels for VREF= lines. The valid values for n and the corresponding label placements are shown in the following table:
|
Table 16.40 lists reference line options that are available when you use ODS graphics.
Table 16.40: Reference Line Options for ODS Graphics
Option |
Option Description |
---|---|
LREF <(INTERSECT)>=value-list |
Requests reference lines perpendicular to the lifetime axis. If (INTERSECT) is specified, a second reference line is drawn perpendicular to the probability axis and intersects the fit line at the same point as the lifetime axis reference line. If a lifetime axis reference line label is specified, the intersecting probability axis reference line is labeled with the probability axis value. |
LREFLABELS =(’label1’ …’labeln’) |
Specifies labels for LREF= lines. |
PREF <(INTERSECT)>=value-list |
Specifies reference lines perpendicular to the probability axis. If (INTERSECT) is specified, a second reference line is drawn perpendicular to the lifetime axis and intersects the fit line at the same point as the probability axis reference line. If a probability axis reference line label is specified, the intersecting lifetime axis reference line is labeled with the lifetime axis value. |
PREFLABELS=(’label1’ …’labeln’) |
Specifies labels for PREF= lines. |
Table 16.41 lists options that control the appearance of the text when you use traditional graphics. These options are not available if ODS Graphics is enabled.
Table 16.41: Text Enhancement Options
Option |
Option Description |
---|---|
FONT=font |
Specifies a software font for text. |
HEIGHT=value |
Specifies the height of text used outside framed areas. |
INFONT=font |
Specifies a software font for text inside framed areas. |
INHEIGHT=value |
Specifies the height of text inside framed areas. |
Table 16.42 lists options that control the appearance of the axes when you use traditional graphics.
Table 16.42: Axis Options for Traditional Graphics
Option |
Option Description |
---|---|
LAXIS=value1 to value2<by value3> |
Specifies tick mark values for the lifetime axis. value1, value2, and value3 must be numeric, and value1 must be less than value2. The lower tick mark is value1. Tick marks are drawn at increments of value3. The last tick mark is the greatest value that does not exceed value2. If value3 is omitted, a value of 1 is used. This method of specification of tick marks is not valid for logarithmic axes. Examples of LAXIS= lists are laxis = -1 to 10 laxis = 0 to 200 by 10 |
LGRID=number |
Specifies a line style for all grid lines. The number is between 1 and 46 and specifies a linestyle for grids. |
LIFELOWER | LLOWER=number |
Specifies the lower limit on the lifetime axis scale. The LLOWER option specifies number as the lower lifetime axis tick mark. The tick interval and the upper lifetime axis limit are determined automatically. This option has no effect if the LAXIS option is used. |
LIFEUPPER | LUPPER=number |
Specifies the upper limit on the lifetime axis scale. The LUPPER option specifies number as the upper lifetime axis tick mark. The tick interval and the lower lifetime axis limit are determined automatically. This option has no effect if the LAXIS option is used. |
MPGRID |
Adds a minor grid for the probability axis. |
MINORLOGGRID |
Adds a minor grid for log axes. |
NOGRID |
Suppresses grid lines. |
NOLLABEL |
Suppresses label for life, or analysis variable, axis. |
NOLTICK |
Suppresses tick marks and tick mark labels for lifetime or analysis variable axis. |
NOPLABEL |
Suppresses label for probability axis. |
NOPTICK |
Suppresses tick marks and tick mark labels for the probability axis. |
NTICK=number |
Specifies the number of tick intervals for the lifetime axis. This option has no effect if the LAXIS option is used. |
PCTLOWER | PLOWER=number |
Specifies the lower limit on probability axis scale. |
PCTUPPER | PUPPER=number |
Specifies the upper limit on probability axis scale. |
PAXISLABEL=‘string’ |
Specifies a label for the probability axis. |
WAXIS=n |
Specifies the line thickness for axes and frame. |
Table 16.43 lists options that control the appearance of the axes when you use ODS Graphics.
Table 16.43: Axis Options for ODS Graphics
Option |
Option Description |
---|---|
LAXIS=value1 to value2<by value3> |
Specifies tick mark values for the lifetime axis. value1, value2, and value3 must be numeric, and value1 must be less than value2. The lower tick mark is value1. Tick marks are drawn at increments of value3. The last tick mark is the greatest value that does not exceed value2. If value3 is omitted, a value of 1 is used. This method of specification of tick marks is not valid for logarithmic axes. Examples of LAXIS= lists are laxis = -1 to 10 laxis = 0 to 200 by 10 |
LIFELOWER | LLOWER=number |
Specifies the lower limit on the lifetime axis scale. The LLOWER option specifies number as the lower lifetime axis tick mark. The tick interval and the upper lifetime axis limit are determined automatically. This option has no effect if the LAXIS option is used. |
LIFEUPPER | LUPPER=number |
Specifies the upper limit on the lifetime axis scale. The LUPPER option specifies number as the upper lifetime axis tick mark. The tick interval and the lower lifetime axis limit are determined automatically. This option has no effect if the LAXIS option is used. |
MINORLOGGRID |
Adds a minor grid for log axes. |
NOGRID |
Suppresses grid lines. |
PCTLOWER | PLOWER=number |
Specifies the lower limit on probability axis scale. |
PCTUPPER | PUPPER=number |
Specifies the upper limit on probability axis scale. |
PAXISLABEL=‘string’ |
Specifies a label for the probability axis. |
Table 16.44 lists options that control colors and patterns used in the graph when you use traditional graphics. These options are not available if ODS Graphics is enabled.
Table 16.44: Color and Pattern Options
Option |
Option Description |
---|---|
CAXIS=color |
Color for axis |
CCENSOR=color |
Color for filling censor plot area |
CENCOLOR=color |
Color for censor symbol |
CFIT=color | (color list) |
color for fit lines and confidence curves in a probability plot |
CFRAME=color |
Color for frame |
CFRAMESIDE=color |
Color for filling frame for row labels |
CFRAMETOP=color |
Color for filling frame for column labels |
CGRID=color |
Color for grid lines |
CHREF=color |
Color for HREF= lines |
CTEXT=color |
Color for text |
CVREF=color |
Color for VREF= lines |
PPOSCOLOR=color | (color list) |
Colors of symbols that represent failures on a probability plot |
Table 16.45 lists options that control the use of a graphics catalog to store graphs if you use traditional graphics. These options are not available if ODS Graphics is enabled.
Table 16.45: Graphics Catalog Options
Option |
Option Description |
---|---|
DESCRIPTION=‘string’ |
Description for graphics catalog member |
NAME=‘string’ |
Name for plot in graphics catalog |