PROC LOGISTIC often overrides all ref= statements when used with a multinomial model. Can SAS output results or a dataset indicating which reference category was selected for the outcome (dependent) variable? The highest category is generally selected by default, but it would be nice to have output to confirm this, particularly if one wishes to change the reference category and confirm that it has changed. For example, can this be determined using the outputted OUTMODEL dataset? The model in question is a (partial) proportional odds cumulative logit model with three different categories (although this applies to any predictor with at least three categories). This is SAS version 9.4M7. Code is: proc logistic data=datain order=internal outest=testout_est outmodel=testout_model;
class outcome(ref=first) catvar1(ref=first) catvar2(ref=last) / param=ref ref=first; * param=effect is default, which compares average effect across all values. param=ref compares to reference category;
model outcome(event='1') = catvar1 catvar2 / link=clogit unequalslopes=(catvar1);
run; This returns the following notes: NOTE: The REF= option for the response variable is ignored. NOTE: PROC LOGISTIC is fitting the cumulative logit model. The probabilities modeled are summed over the responses having the lower Ordered Values in the Response Profile table. OUTMODEL output (testout_model). Some _MISC_ values have been changed slightly or replaced with xxx. _TYPE_ _NAME_ _CATEGORY_ _NAMEIDX_ _CATIDX_ _MISC_ L 7 M NYYNYNNN 7 G outcome outcome=0 0 0 10 G outcome outcome=1 0 1 10 G outcome outcome=2 0 2 -10 G outcome -1 0 13 G outcome -1 1 8 G outcome -1 2 35 G outcome -1 -2 -16 G catvar1 1 1 0 -1 G catvar1 2 1 1 1 G catvar1 -2 -1 3 G catvar1 -2 -2 -6 G catvar2 1 2 0 2 G catvar3 2 2 1 2 G catvar4 3 2 2 -2 G catvar5 -3 -1 3 G catvar6 -3 -2 -11 E Intercept E 0 0 xxx E Intercept E 0 1 xxx E EFFECT G 0 0 1 E EFFECT X 0 0 1 E EFFECT E 0 0 xxx E EFFECT E 0 1 xxx E EFFECT Q 0 0 0 E EFFECT G 1 0 3 E EFFECT X 1 0 3 E EFFECT E 1 0 xxx E EFFECT E 1 1 xxx E EFFECT Q 1 1 1 E EFFECT V 0 xxx E EFFECT V 1 xxx E EFFECT V 2 xxx E EFFECT V 3 xxx E EFFECT V 4 xxx E EFFECT V 5 xxx E EFFECT V 6 xxx E EFFECT V 7 xxx E EFFECT V 8 xxx E EFFECT V 9 xxx E EFFECT V 10 xxx E EFFECT V 11 xxx E EFFECT V 12 xxx E EFFECT V 13 xxx E EFFECT V 14 xxx E EFFECT V 15 xxx E EFFECT V 16 xxx E EFFECT V 17 xxx E EFFECT V 18 xxx E EFFECT V 19 xxx E EFFECT V 20 xxx X 52 27 232 xxx
... View more
