The RAREEVENTS Procedure(Experimental)

CHART Statement

CHART process-variable < $*$ index-variable> < / options>;

The CHART statement produces a rare events chart. The process-variable contains measurements of times between events. You can use the optional index-variable to label the tick marks on the chart’s horizontal axis. If you specify a numeric index-variable, its values must be in ascending order in the input data: the procedure does not sort its input. When you do not specify an index variable, the tick marks on the horizontal axis are numbered sequentially, starting with 1.

Table 16.1 summarizes the options available in the CHART statement.

Table 16.1: CHART Statement Options

Option	Description
ALPHALPL=	Specifies the probability that is used to compute the lower probability limit
ALPHAUPL=	Specifies the probability that is used to compute the upper probability limit
DIST=	Specifies the distribution that is used to compute probability limits
EXCHART	Specifies that a chart be displayed only if there are points outside the probability limits
NOCHART	Suppresses creation of the rare events chart
NOHLABEL	Suppresses the horizontal axis label of the chart
NOVLABEL	Suppresses the vertical axis label of the chart
NPANELPOS=	Specifies the number of horizontal axis plotting positions per panel
ODSFOOTNOTE=	Adds a footnote to the chart
ODSFOOTNOTE2=	Adds a secondary footnote to the chart
ODSTITLE=	Specifies a title for the chart
ODSTITLE2=	Specifies a secondary title for the chart
OUTLIMITS=	Creates a SAS data set that contains probability limits for the chart
OUTTABLE=	Creates a SAS data set that contains a summary of the rare events chart
TOTPANELS=	Specifies the number of panels that are used to display the chart

You can specify the following options only in the CHART statement. For detailed descriptions of options common to the CHART and COMPARE statements, see the section Common CHART and COMPARE Statement Options.

ALPHALPL= $\alpha _{\mr{LPL}}$

specifies the probability ( $0 < \alpha _{\mr{LPL}}< 1$ ) that is used to compute the lower probability limit (LPL) for the rare events chart, based on the probability distribution that you specify in the DIST= option. The LPL is computed so that the probability of a measurement from the distribution being less than the LPL is $\alpha _{\mr{LPL}}$ . By default, $\alpha _{\mr{LPL}}=0.005$ .

With a discrete probability distribution, it is not possible in general to compute a LPL for which this probability is exactly $\alpha _{\mr{LPL}}$ . In that case, the chart includes a legend that shows the $\alpha _{\mr{LPL}}$ that corresponds to the computed LPL.

ALPHAUPL= $\alpha _{\mr{UPL}}$

specifies the probability ( $0 < \alpha _{\mr{UPL}}< 1$ ) that is used to compute the upper probability limit (UPL) for the rare events chart, based on the probability distribution that you specify in the DIST= option. The UPL is computed so that the probability of a measurement from the distribution being greater than the UPL is $\alpha _{\mr{UPL}}$ . By default, $\alpha _{\mr{UPL}}=0.005$ .

With a discrete probability distribution, it is not possible in general to compute a UPL for which this probability is exactly $\alpha _{\mr{UPL}}$ . In that case, the chart includes a legend that shows the $\alpha _{\mr{UPL}}$ that corresponds to the computed UPL.

EXCHART<(LOWER | UPPER)>

specifies that a rare events chart be displayed only when one or more measurements lie outside the probability limits. If you specify EXCHART(LOWER), then a chart is displayed only when a measurement is less than the lower probability limit. If you specify EXCHART(UPPER), then a chart is displayed only when a measurement is greater than the upper probability limit.

NOCHART

suppresses display of the rare events chart. You can use the NOCHART option together with the OUTLIMITS= or OUTTABLE= option to create output data sets without displaying a chart.

NPANELPOS=n NPANEL=n

specifies the number of horizontal axis plotting positions per panel in the chart. You usually specify this option to display more points in a panel than the default number, which is 50.

You can specify a positive or negative value for n. The absolute value of n must be at least 5. If n is positive, the number of positions is adjusted so that it is approximately equal to n and so that all panels display approximately the same number of positions. If n is negative, then no balancing is done, and each panel (except possibly the last) displays approximately $|n|$ positions.

OUTLIMITS=SAS-data-set

creates an output SAS data set that contains the probability limits and related information for the rare events chart. For more information about the OUTLIMITS= data set, see the section OUTLIMITS= Data Set.

OUTTABLE=SAS-data-set

creates an output SAS data set that contains the information plotted in the rare events chart, including the process measurements and the probability limits. For more information about the OUTTABLE= data set, see the section OUTTABLE= Data Set.

TOTPANELS=n

specifies the number of panels that are used to display the chart. By default, the number of panels is determined by the value that you specify in the NPANELPOS= option. If you specify both the TOTPANELS= and NPANELPOS= options, the TOTPANELS= value takes precedence.