Reading Preestablished Control Limits

BOXCHART Statement

Reading Preestablished Control Limits

See SHWBOXA in the SAS/QC Sample Library

In the previous example, the OUTLIMITS= data set TURBLIM saved control limits computed from the measurements in TURBINE. This example shows how these limits can be applied to new data. The following statements create the box chart in Figure 32.11 using new measurements in a data set named TURBINE2 (not listed here) and the control limits in TURBLIM:

   title 'Box Chart for Power Output';
   symbol v=dot c=salmon;
   proc shewhart data=turbine2 limits=turblim;
      boxchart kwatts*day / cframe   = vligb
                            cboxfill = ywh
                            cboxes   = dagr
                            cinfill  = ligr;
   run;

The LIMITS= option in the PROC SHEWHART statement specifies the data set containing the control limits. By default,^* this information is read from the first observation in the LIMITS= data set for which

the value of _VAR_ matches the process name KWATTS
the value of _SUBGRP_ matches the subgroup-variable name DAY

The chart reveals an increase in variability beginning on August 1.

Figure 32.11: Box Chart for Second Set of Power Outputs

In this example, the LIMITS= data set was created in a previous run of the SHEWHART procedure. You can also create a LIMITS= data set with the DATA step. See "LIMITS= Data Set" for details concerning the variables that you must provide.

Chapter Contents
Previous
Next
Top