PROC LOGISTIC CONTRAST STATEMENTS

[tka726]

Hello!

I'm trying to write some contrast statements in proc logistic.  The dependent variable is event (0,1) and the independent variable is quintile, which has 5 categories (0, 1, 2, 3, 4). I want the value of 2 to be the reference, but also want to compare other quintiles.  

PROC LOGISTIC DATA=origs descending;
CLASS  quint(ref="2")/param=ref;
model event= quint;

contrast '0vs2' quint  1  0  0  0  -1 /estimate=both;
contrast '1vs2' quint  0  1  0  0  -1 /estimate=both;
contrast '3vs2' quint  0  0  1  0  -1 /estimate=both;
contrast '4vs2' quint  0  0  0  1  -1 /estimate=both;

I found that the contrast statements above yield the same results as the model output (with 2 as the reference), but I can not figure out how to write contrast statements to compare, say quintile 3 vs 4. Any thoughts?

[StatDave · Accepted solution]

It's always best to avoid the CONTRAST and ESTIMATE statements when other statements that don't require specifying contrast coefficients can do what you want. In this case, you probably just need a single LSMEANS statement. Note the change of PARAM= to GLM.

PROC LOGISTIC DATA=origs descending;
CLASS  quint(ref="2")/param=glm;
model event= quint;

lsmeans quint / diff oddsratio;

run;

[tka726]

This is perfect, thank you!