CDFPLOT Statement: CAPABILITY Procedure

Overview: CDFPLOT Statement

The CDFPLOT statement plots the observed cumulative distribution function (cdf) of a variable, defined as

$\begin{eqnarray*} F_{N}(\Mathtext{x}) & = & \mbox{percent of nonmissing values} \leq \Mathtext{x} \\ & = & \frac{\mbox{number of values} \leq x}{N} \times 100\% \end{eqnarray*}$

where N is the number of nonmissing observations. The cdf is an increasing step function that has a vertical jump of $\frac{1}{N}$ at each value of x equal to an observed value. The cdf is also referred to as the empirical cumulative distribution function (ecdf).

You can use options in the CDFPLOT statement to do the following:

superimpose specification limits
superimpose fitted theoretical distributions
specify graphical enhancements (such as color or text height)

You can also create a comparative cdf plot by using the CDFPLOT statement in conjunction with a CLASS statement.

You have three alternatives for producing cdf plots with the CDFPLOT statement:

ODS Graphics output is produced if ODS Graphics is enabled, for example by specifying the ODS GRAPHICS ON statement prior to the PROC statement.
Otherwise, traditional graphics are produced by default if SAS/GRAPH^®is licensed.
Legacy line printer charts are produced when you specify the LINEPRINTER option in the PROC statement.

See Chapter 3: SAS/QC Graphics, for more information about producing these different kinds of graphs.