I was wondering how to specify the gamma distribution's canonical negative inverse link in the PROC GENMOD procedure.
When I tried leaving "LINK" blank, I saw that SAS automatically implemented a POWER(-1) link. However, to my understanding, that is akin to the inverse, and not a negative inverse link.
data clots;
input u y;
x=log(u);
datalines;
5 118
10 58
15 42
20 35
30 27
40 25
60 21
80 19
100 18
;
run;
*default POWER(-1);
proc genmod data=clots;
model y = x / dist=gamma
link = POWER(-1);
output out = Residuals
pred = Pred;
run;
*user-defined -POWER(-1);
proc genmod data=clots;
model y = x / dist=gamma;
fwdlink link = -1*_MEAN_**-1;
invlink ilink = -1*_XBETA_**-1;
output out = Residuals
pred = Pred;
run;
Take a look at the parameter estimates!
-unison
-unison
The 2025 SAS Hackathon Kicks Off on June 11!
Watch the live Hackathon Kickoff to get all the essential information about the SAS Hackathon—including how to join, how to participate, and expert tips for success.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.