Date:         Wed, 17 Oct 2007 13:59:35 -0400
Reply-To:     DJR <rizzolod@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         DJR <rizzolod@HOTMAIL.COM>
Subject:      help with an estimate statement in GENMOD
Content-Type: text/plain; charset=ISO-8859-1

Hello SAS-L subscribers:

I am trying to output an estimate from a generalized linear model fit in SAS
GENMOD.  The model relates the binary response to a continuous variable
(time, in minutes: 1,2,...,60) and a categorical variable with 3 levels
(STAGE, listed in a class statement).  The specific model of interest is:

model Y = time  time*time  time*STAGE  time*time*STAGE / dist=B link=logit LRCI;

My goal is get an estimate of the response over a range of times with the
STAGE effects averaged-out. I am using an estimate statement to attempt
this. For example, at time=1, I have written the estimate statement as follows:

estimate “time=1” intercept  1
    time   1
    time*time  1
    time*STAGE  0.33 0.33 0.33
    time*time*STAGE 0.33  0.33 0.33;

for time=2:

estimate “time=2” intercept  1
    time   2
    time*time  4
    time*STAGE  0.66 0.66 0.66
    time*time*STAGE 1.33  1.33 1.33;

and I repeat this across the range of times I am interested in. I get the
estimates that I am after, except for the value of time=1, which gives “no
est.” I have used this code with similar data before.  Because, the code
works (or seems to work) for other values of time, I suspected it was a
problem with the dataset, but I checked it and found no errors.  Is this
approach to averaging out the stage effect correct (i.e., the coefficient in
the estimate statement being set to the value of time*time*0.333), and if
so, what might the problem at the of value time=1 be?
Thanks for the help.
DJR