SPECHART Statement

SPECHART < / options> ;

The SPECHART statement produces an SPE chart based on a principal components model computed by the MVPMODEL procedure. In a Phase I analysis, the SPE statistics are computed by the MVPMODEL procedure and read from the HISTORY= data set. In a Phase II analysis, the SPE statistics are computed by the MVPMONITOR procedure from information about the principal components model which is specified in the LOADINGS= data set.

You can specify the following options after a slash (/):

ALPHA=value

specifies the probability used to compute control limits for the SPE chart. If you specify ALPHA=, the control limits are computed so that the probability is that the SPE statistic exceeds its control limits. The value of can range between 0 and 1. By default, is 0.05.

CONTRIBUTIONS <(contribution-options)>

creates a contribution plot for each point outside the control limits of the SPE chart. You can specify the following contribution-options in parentheses following the CONTRIBUTIONS option:

MAXNPLOTS=n

specifies the maximum number, n, of contribution plots produced. When n is less than the number of points outside the control limits, contribution plots are produced for the first n out-of-control points.

MAXNVARS=n

specifies that only the n contributions with the greatest magnitudes be displayed in the contribution plots. For each out-of-control point, the n variables that contribute the most at that point are displayed. By default, all variable contributions are displayed.

EXCHART

specifies that an SPE chart be created only when one or more points lie outside the control limits.

NOCHART

suppresses creation of the SPE chart. You typically specify the NOCHART option when you use the OUTTABLE= option to save results to an output data set. You can also use the NOCHART option along with the CONTRIBUTIONS option to produce contribution plots for out-of-control points without displaying the SPE chart.

NPANELPOS=n
NPANEL=n

specifies the number of horizontal axis plotting positions per panel of the SPE chart. A panel is defined as a screen or page. You typically specify the NPANELPOS= option to display more points on a panel than the default number, which is 50.

You can specify a positive or negative number for n. The absolute value of n must be at least 5. If n is positive, the number of positions is adjusted so that it is approximately equal to n and so that all panels display approximately the same number of positions. If n is negative, no balancing is done and each panel (except possibly the last) displays approximately n positions.

OUTTABLE=SAS-data-set

creates an output SAS data set that saves the information plotted on the SPE chart, including the SPE statistic values and control limits. See the section OUTTABLE= Data Set for a description of the OUTTABLE= data set.


Note: This procedure is experimental.