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MCHART Statement 
See SHWMCHR in the SAS/QC Sample Library 
The previous example illustrates how you can create median charts using raw data (process measurements). However, in many applications the data are provided as subgroup summary statistics. This example illustrates how you can use the MCHART statement with data of this type.
The following data set (DETSUM) provides the data from the preceding example in summarized form. There is exactly one observation for each subgroup (note that the subgroups are still indexed by LOT). The variable WEIGHTM contains the subgroup medians, the variable WEIGHTR contains the subgroup ranges, and the variable WEIGHTN contains the subgroup sample sizes (these are all five).
data detsum; input lot weightm weightr; weightn = 5; datalines; 1 22.56 9.54 2 23.54 3.07 3 24.35 4.65 4 25.52 5.05 5 23.25 8.04 6 23.01 6.33 7 24.19 2.19 8 26.27 2.18 9 22.31 6.08 10 22.66 8.21 11 26.38 4.97 12 23.01 5.05 13 23.15 5.37 14 24.73 4.95 15 25.86 5.58 16 23.99 4.35 17 24.30 5.24 18 24.88 4.87 19 25.92 7.22 20 25.63 6.30 21 25.17 6.52 22 26.72 5.18 23 23.67 9.17 24 24.92 4.62 25 24.51 5.40 26 24.75 3.41 27 25.10 4.76 28 25.64 3.47 ;A listing of DETSUM is shown in Figure 35.3.
You can read this data set by specifying it as a HISTORY= data set in the PROC SHEWHART statement, as follows:
title 'Median Chart for Weights'; proc shewhart history=detsum lineprinter; mchart weight*lot='*'; run;
Note that WEIGHT is not the name of a SAS
variable in the data set DETSUM but is, instead,
the common prefix for the names
of the three SAS variables WEIGHTM, WEIGHTR, and WEIGHTN.
The suffix characters M, R, and N indicate
median, range, and sample size, respectively.
Thus, you can specify three subgroup summary variables in the
HISTORY= data set with a single name (WEIGHT), which is referred to
as the process. The name LOT specified after the asterisk
is the name of the subgroupvariable.

In general, a HISTORY= input data set used with the MCHART
statement must contain the following variables:
Furthermore, the names of the subgroup median, range (or standard deviation), and sample size variables must begin with the process name specified in the MCHART statement and end with the special suffix characters M, R (or S), and N, respectively. If the names do not follow this convention, you can use the RENAME option in the PROC SHEWHART statement to rename the variables for the duration of the SHEWHART procedure step (see "Creating Charts for Medians and Ranges from Summary Data" ).
If you specify the STDDEVIATIONS option in the MCHART statement,
the HISTORY= data set must contain a subgroup standard deviation
variable; otherwise, the HISTORY= data set must contain a subgroup
range variable.
The STDDEVIATIONS option specifies that the estimate
of the process standard deviation is to be
calculated from subgroup standard deviations rather
than subgroup ranges.
For example, in the following statements, the data set
DETSUM2 must contain a subgroup standard deviation
variable named WEIGHTS:
title 'Median Chart for Weights'; symbol v=dot; proc shewhart history=detsum2; mchart weight*lot / stddeviations; run;
Options such as STDDEVIATIONS are specified after the slash (/) in the MCHART statement. A complete list of options is presented in the "Syntax" section.
In summary, the interpretation of process depends on the
input data set.
For more information, see "HISTORY= Data Set" .
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