The SHEWHART Procedure

Axis Labels

You can specify axis labels by assigning labels to particular variables in the input data set:

The label associated with the subgroup variable is used as the horizontal axis label.
When you specify a DATA= input data set, the label associated with the process variable is used as the vertical axis label.
Otherwise, the variable whose label is used on the vertical axis depends on whether you specify a HISTORY= or TABLE= input data set, as summarized in Table 18.71, where Process is the process variable name.

Table 18.71: Labeling Chart Axes

Chart	HISTORY= Data	TABLE= Data
Statement(s)	Set Variable	Set Variable
BOXCHART, XCHART, XRCHART, XSCHART	Subgroup mean variable, ProcessX	`_SUBX_`
BOXCHART with CONTROLSTAT= MEDIAN	Subgroup median variable, ProcessM	`_SUBMED_`
CCHART	Subgroup defects per unit variable, ProcessU	`_SUBC_`
IRCHART	Subgroup measurement variable, Process	`_SUBI_`
MCHART, MRCHART	Subgroup median variable, ProcessM	`_SUBMED_`
NPCHART	Subgroup proportion nonconforming variable, ProcessP	`_SUBNP_`
PCHART	Subgroup proportion nonconforming variable, ProcessP	`_SUBP_`
RCHART	Subgroup range variable, ProcessR	`_SUBR_`
SCHART	Subgroup standard deviation variable, ProcessS	`_SUBS_`
UCHART	Subgroup defects per unit variable, ProcessU	`_SUBU_`

When you specify an IRCHART, MRCHART, XRCHART, or XSCHART statement, or the TRENDVAR= option in a BOXCHART, MCHART, or XCHART statement, primary and secondary charts are produced. You can provide distinct labels for the primary and secondary vertical axes by specifying a label that contains a split character in the SPLIT= option. The portion of the label before the split character labels the primary vertical axis, and the portion after the split character labels the secondary vertical axis.

For example, the following sets of statements specify the label "Avg Diameter in mm" for the vertical axis of the $\bar{X}$ chart and the label "Range in mm" for the vertical axis of the R chart:

proc shewhart data=Wafers;
   xrchart Diameter*Batch / split = '/' ;
   label Diameter = 'Avg Diameter in mm/Range in mm';
run;

proc shewhart history=Wafersum;
   xrchart Diameter*Batch / split = '/' ;
   label DiameterX = 'Avg Diameter in mm/Range in mm';
run;

proc shewhart table=Wafertab;
   xrchart Diameter*Batch / split = '/' ;
   label _SUBX_ = 'Avg Diameter in mm/Range in mm';
run;

In this example, the label assignments are in effect only for the duration of the procedure step, and they temporarily override any permanent labels associated with the variables.

For more information, see Labeling Axes.