XCHART Statement: SHEWHART Procedure

Saving Summary Statistics

See SHWXCHR in the SAS/QC Sample LibraryIn this example, the XCHART statement is used to create a summary data set that can be read later by the SHEWHART procedure (as in the preceding example). The following statements read measurements from the data set Partgaps and create a summary data set named Gaphist:

proc shewhart data=Partgaps;
   xchart Partgap*Sample / outhistory = Gaphist

The OUTHISTORY= option names the output data set, and the NOCHART option suppresses the display of the chart, which would be identical to the chart in Figure 17.96.

Figure 17.99 contains a partial listing of Gaphist.

Figure 17.99: The Summary Data Set Gaphist

Summary Data Set for Gap Widths

Sample PartgapX PartgapR PartgapN
1 270 35 5
2 258 25 5
3 248 24 5
4 260 39 5
5 273 29 5

There are four variables in the data set Gaphist.

  • Sample contains the subgroup index.

  • PartgapX contains the subgroup means.

  • PartgapR contains the subgroup ranges.

  • PartgapN contains the subgroup sample sizes.

Note that the summary statistic variables are named by adding the suffix characters X, R, and N to the process Partgap specified in the XCHART statement. In other words, the variable naming convention for OUTHISTORY= data sets is the same as that for HISTORY= data sets.

If you specify the STDDEVIATIONS option, the OUTHISTORY= data set includes a subgroup standard deviation variable rather than a subgroup range variable, as demonstrated by the following statements:

proc shewhart data=Partgaps;
   xchart Partgap*Sample / outhistory = Gaphist2

Figure 17.100 contains a partial listing of Gaphist2.

Figure 17.100: The Summary Data Set Gaphist2

Summary Data Set with Subgroup Standard Deviations

Sample PartgapX PartgapS PartgapN
1 270 12.6293 5
2 258 10.2225 5
3 248 10.6771 5
4 260 14.2302 5
5 273 11.2027 5

The variable PartgapS, which contains the subgroup standard deviations, is named by adding the suffix character S to the process Partgap.

For more information, see OUTHISTORY= Data Set.