Reading Individual Measurements and Moving Ranges

IRCHART Statement

Reading Individual Measurements and Moving Ranges

See SHWIR1 in the SAS/QC Sample Library

In some applications, both individual measurements and moving ranges may be provided. You can read this type of data set by specifying it with the HISTORY= option in the PROC SHEWHART statement. For example, the following statements read the data set JETINFO (see Figure 34.3) and create the charts shown in Figure 34.4:

   title 'Individual Measurements and Moving Range Charts';
   proc shewhart history=jetinfo lineprinter;
      irchart diam*engine='*';
   run;

Note that the charts are produced on a line printer since the LINEPRINTER option is specified in the PROC SHEWHART statement. ^* The asterisk (*) specified in single quotes after the subgroup-variable indicates the character used to plot points. This character must follow an equal sign.

Individual Measurements and Moving Range Charts

                                                                      3 Sigma Limits
                                                                      For n=2:      
       -------------------------------------------------------------                
  100 +                                                             |               
      |                                                             |               
      |=============================================================| UCL = 94.6    
   90 +                                               +*            |               
d     |                                             *+  +           |               
i     |        +*+      +*     *             +*+  ++     +   *+   +*| -             
a  80 +---*++*+---+*++*+--+---+-++---------*+---+*-------+-++--+*+--| X = 80.4      
m     |                    + +    *++*    +               *         |               
      |                     *         ++ +                          |               
   70 +                                 *                           |               
      |=============================================================| LCL = 66.2    
      |                                                             |               
   60 +                                                             |               
       +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+                
       -------------------------------------------------------------                
M  20 +                                                             |               
v     |=============================================================| UCL = 17.4    
g  15 +                                                             |               
      |                                                   *         |               
R  10 +                     *++*+         +*             + +        |               
a     |                    +     +*     *+  +       *+  +   +       | -             
n   5 +--------+*++*+-----+--------++-++-----+----++--+*-----*+-----| R = 5.3       
g     |      *+      +*++*           *        *++*             +*++*|               
e   0 +=============================================================| LCL = 0       
       +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+                
       0     2     4     6     8    10    12    14    16    18    20                
                                                                                    
                               Engine Number

Figure 34.4: Charts from the Summary Data Set JETINFO

A HISTORY= data set used with the IRCHART statement must contain the following variables:

subgroup variable
individual measurements variable
moving range variable

Furthermore, the name of the moving range variable must begin with the process name specified in the IRCHART statement and end with the special suffix character R. If the name does not follow this convention, you can use the RENAME option in the PROC SHEWHART statement to rename this variable for the duration of the procedure step (see "Creating Charts for Means and Ranges from Summary Data" ). For more information, see "HISTORY= Data Set" .

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