--- On Fri, 6/26/09, Jose <jsotosh@GMAIL.COM> wrote:

> From: Jose <jsotosh@GMAIL.COM> > Subject: code for categorical predictor variables > To: SAS-L@LISTSERV.UGA.EDU > Date: Friday, June 26, 2009, 2:27 PM > > Hi, > > I am running a logistic regression with categorical predictor > variables, for these I need to model the reference levels as 1 0, not > 0 1 (the default reference level for categorical predictor variables). > I can’t find the code to change the default reference level. Can > anyone give me this code? Thank you. >

Jose,

You don't state what version of SAS you have available. I will assume that you have 9.x. The CLASS statement of PROC LOGISTIC in recent SAS versions supports a REF=?? option. In order to specify the value 0 as the reference level when X takes on values 0 or 1, you can specify the option REF=FIRST. Thus, your code would look something like:

proc logistic data=mydata; class x(ref=first); model y = x; run;

The above code uses a variable-specific option. You can also specify that all variables should use the first level as the reference level as follows:

proc logistic data=mydata; class x / ref=first; model y = x; run;

HTH,

Dale

--------------------------------------- Dale McLerran Fred Hutchinson Cancer Research Center mailto: dmclerra@NO_SPAMfhcrc.org Ph: (206) 667-2926 Fax: (206) 667-5977 ---------------------------------------