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NPCHART Statement

Syntax

The basic syntax for the NPCHART statement is as follows:

NPCHART process*subgroup-variable ;

The general form of this syntax is as follows:

NPCHART (processes)*subgroup-variable <(block-variables ) >
< =symbol-variable | ='character' > < / options >;


You can use any number of NPCHART statements in the SHEWHART procedure. The components of the NPCHART statement are described as follows.

process
processes
identify one or more processes to be analyzed. The specification of process depends on the input data set specified in the PROC SHEWHART statement.



A process is required. If you specify more than one process, enclose the list in parentheses. For example, the following statements request distinct np charts for REJECTS and REWORKS:

  proc shewhart data=measures;
     npchart (rejects reworks)*sample / subgroupn=100;
  run;


Note that when data are read from a DATA= data set, the SUBGROUPN= option, which specifies subgroup sample sizes, is required.

subgroup-variable
is the variable that identifies subgroups in the data. The subgroup-variable is required. In the preceding NPCHART statement, SAMPLE is the subgroup variable. For details, see "Subgroup Variables" .

block-variables
are optional variables that group the data into blocks of consecutive subgroups. The blocks are labeled in a legend, and each block-variable provides one level of labels in the legend. See "Displaying Stratification in Blocks of Observations" for an example.

symbol-variable
is an optional variable whose levels (unique values) determine the symbol marker or character used to plot numbers of nonconforming items.



character
specifies a plotting character for charts produced on line printers. For example, the following statements create an np chart using an asterisk (*) to plot the points:

   proc shewhart data=values;
      npchart rejects*day='*' / subgroupn=100;
   run;


options
enhance the appearance of the chart, request additional analyses, save results in data sets, and so on. The "Summary of Options" section, which follows, lists all options by function. Chapter 46, "Dictionary of Options," describes each option in detail.


Summary of Options

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