This usage note provides various ways of scoring a new data set --
http://support.sas.com/kb/33307
Here is an example of Approach 3. Augmenting the training data set for your case:
1. create a scoring data set, for example, NEW, that contains the fixed values for other covariates and the plotting values for the ones you are interested in plotting. Make sure the dependent variable has missing values in this data set;
2. combine the original data set with this scoring data set (NEW) with a SET statement in a SAS data step.
3. Use PROC MIXED to fit your model on this combined data set. Make sure you use the OUTP= option in the MODEL statement.
The observations from step 2 have missing values for the dependent variable, therefore will not be used in the model fitting. However, they will get predicted values. You will then use PROC SGPLOT to plot these observations.
Alternatively, you might use the data set NEW as the scoring data in PROC PLM to get the predicted values, then use PROC SGPLOT to plot it. This is basically approach 1 in the usage note linked above.
Hope this helps,
Jill
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