Labeling the Vertical Axis

You can specify a label for the vertical axis of a primary chart by using a LABEL statement to assign the label to a particular variable in the input data set. The type of input data set, the chart statement, and the process specified in the chart statement determine which variable to use in the LABEL statement.

• If the input data set is a DATA= data set, assign the label to the process variable (process) specified in the chart statement.

• If the input data set is a HISTORY= data set, assign the label to the variable specified in the chart statement whose name begins with the prefix process and ends with the appropriate suffix given by the following list:

  Chart Statement	Suffix
  BOXCHART with CONTROLSTAT=MEAN	X
  BOXCHART with CONTROLSTAT=MEDIAN	M
  CCHART	U
  IRCHART	none
  MCHART	M
  MRCHART	M
  NPCHART	P
  PCHART	P
  RCHART	R
  SCHART	S
  UCHART	U
  XCHART	X
  XRCHART	X
  XSCHART	X

  If the prefix process consists of 32 characters, shorten the prefix to its first 16 characters and last 15 characters before adding the suffix.

• If the input data set is a TABLE= data set, assign the label to the predefined variable given by the following table:

  Chart Statement	Variable
  BOXCHART with CONTROLSTAT=MEAN	_SUBX_
  BOXCHART with CONTROLSTAT=MEDIAN	_SUBMED_
  CCHART	_SUBC_
  IRCHART	_SUBI_
  MCHART	_SUBMED_
  MRCHART	_SUBMED_
  NPCHART	_SUBNP_
  PCHART	_SUBP_
  RCHART	_SUBR_
  SCHART	_SUBS_
  UCHART	_SUBU_
  XCHART	_SUBX_
  XRCHART	_SUBX_
  XSCHART	_SUBX_

If the chart statement produces primary and secondary charts, as in the case of the XSCHART statement, you can break the label into two parts by including a split character in the label. The part before the split character labels the vertical axis of the primary chart, and the part after the split character labels the vertical axis of the secondary chart. To specify the split character, use the SPLIT= option in the chart statement.

For example, the following statements redisplay the and charts in Figure 13.43.55 with specified labels for the horizontal and vertical axes:

symbol v=none w=1;
title 'Control Chart for Diameter';
proc shewhart history=Parts;
   xschart Diam*Sample / split   = '/';
   label Sample = 'Sample Number'
         DiamX  = 'Average Diameter/Std Deviation';
run;

The charts are displayed in Figure 13.43.56. Because the input data set Parts is a HISTORY= data set, the vertical axes are labeled by assigning a label to the subgroup mean variable DiamX (that is, the process Diam with the suffix X).¹ Assigning a label to Diam would result in an error message since Diam is interpreted as a prefix rather than a SAS variable.

Output 13.43.56 Control Charts with Axis Labels Specified

If the input data set were a DATA= data set rather than a HISTORY= data set, you would associate the label with the variable Diam. If the input data set were a TABLE= data set, you would associate the label with the variable _SUBX_.

For another illustration, see Example 13.17.