Example 3.3: Using LIMITS= Data Set Extensions

The SHEWHART Procedure

Example 3.3: Using LIMITS= Data Set Extensions

The following statements create the HISTORY= data set flange, containing means and ranges of flange width measurements for subgroups of size five:

   data flange;
      input day date7. sample 10-11 _phase_ $14-23
            flwidthx flwidthr flwidthn;
      format   day date7.;
   datalines;
   08FEB90   6  Production  0.97360  0.06247  5
   09FEB90   7  Production  1.00486  0.11478  5
   10FEB90   8  Production  1.00251  0.13537  5
   11FEB90   9  Production  0.95509  0.08378  5
   12FEB90  10  Production  1.00348  0.09993  5
   15FEB90  11  Production  1.02566  0.06766  5
   16FEB90  12  Production  0.97053  0.07608  5
   17FEB90  13  Production  0.94713  0.10170  5
   18FEB90  14  Production  1.00377  0.04875  5
   19FEB90  15  Production  0.99604  0.08242  5
   22FEB90  16  Change 1    0.99218  0.09787  5
   23FEB90  17  Change 1    0.99526  0.02017  5
   24FEB90  18  Change 1    1.02235  0.10541  5
   25FEB90  19  Change 1    0.99950  0.11476  5
   26FEB90  20  Change 1    0.99271  0.05395  5
   01MAR90  21  Change 1    0.98695  0.03833  5
   02MAR90  22  Change 1    1.00969  0.06183  5
   03MAR90  23  Change 1    0.98791  0.05836  5
   04MAR90  24  Change 1    1.00170  0.05243  5
   05MAR90  25  Change 1    1.00412  0.04815  5
   08MAR90  26  Change 2    1.00261  0.05604  5
   09MAR90  27  Change 2    0.99553  0.02818  5
   10MAR90  28  Change 2    1.01463  0.05558  5
   11MAR90  29  Change 2    0.99812  0.03648  5
   12MAR90  30  Change 2    1.00047  0.04309  5
   15MAR90  31  Change 2    0.99714  0.03689  5
   16MAR90  32  Change 2    0.98642  0.04809  5
   17MAR90  33  Change 2    0.98891  0.07777  5
   18MAR90  34  Change 2    1.00087  0.06409  5
   19MAR90  35  Change 2    1.00863  0.02649  5
   ;
   run;

This DATA step creates the LIMITS= data set flanlim:

   data flanlim;
      input _index_ $1-10 _lclx_ _mean_ _uclx_ _r_ _uclr_ _stddev_ @;
      input _cframe_ $ _cinfill_ $ _climits_ $ _wlimits_ _llimits_;
      _var_    = 'FLWIDTH ';
      _subgrp_ = 'SAMPLE  ';
      _type_   = 'ESTIMATE';
      _limitn_ = 5;
      _sigmas_ = 3;
      _alpha_  = .0026998;
      _lclr_   = 0;
   datalines;
   Production 0.9379 0.9883 1.0386 0.0873 0.1846 0.03753
              steel ligr red 2 4
   Change 1   0.9617 0.9992 1.0368 0.0651 0.1377 0.02800
              vigb vlib yellow 1 2
   Change 2   0.8709 0.9680 1.0652 0.1684 0.3561 0.07241
              vligb ywh vibg 3 3
   ;
   run;

The variables _CFRAME_, _CINFILL_, _CLIMITS_, _WLIMITS_, and _LLIMITS_ specify colors, line widths, and line types for displaying three different phases. For example, in the `Production' phase the specified frame color is steel, the area between the control limits is light gray, the control limits are red, the control limits width is two pixels, and the control limits line style is 4. The following statements produce the chart shown in Output 3.3.1:

symbol1 v=dot c=black h=0.4;
proc shewhart history=flange limits=flanlim;
   xchart flwidth*sample /
      readphase = all
      readindex = all
      phaselegend;
run;

Output 3.3.1: $\bar{X}$ Chart with Variations in Display of Phases

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