Observed vs predicted plots should be interpreted in the transformed space for transformed responses (Q810)

The information in this article applies to: 
SIMCA 13
SIMCA 14
Symptoms: 

When creating an observed vs predicted plot in SIMCA (Home | Observed vs. predicted or Predict | Y PS) for a transformed response the displayed plot is by default backtransformed to original units. In order to view the correlation between the observed and predicted values, this plot should be interpreted in the transformed space.

Workaround: 

Display the plot in transformed metrics using one of the following methods:

  • Select the vectors in the Plot/List Scatter plot and select the Transform check box before adding the vector (also possible to change after addition by selecting Yes in the Transform column) - RECOMMENDED.
  • In the Model Options dialog (click Options in the Model Window), in the Predictions tab, select the Transform predictions check box. NOTE! A drawback with using this second method is that all y-variables will be displayed as "trans" whether a transformation was specified or not AND plots like the Contour plot are also displayed in transformed metrics.
More Information: 

Note that the above is also true for the normal probability plot of residuals (Analyze | Residuals N-plot). NOTE that the displayed vector is YVarResSt.

Date modified: Jan 29, 2015
Article type: 
Problem