[R] Error in geeglm

[leila janani]

Hello everyone,
I want to fit a following model as an alternative to log
binomial model (Thomas Lumley,et al…2006).
But I come across with this error: “ Error in eval(expr,
envir, enclos) : cannot find valid starting values: please specify some”
geeglm (outcome ~ treatment,
data = dat, family=gaussian(link="log"), id=subject_id)

Using SAS (Genmod) I can run this model without any problem:

proc genmod data=dat
DESCENDING;
model outcome = treatment / dist=normal  link=log;
repeated subject=subject_id;
run; 

Could anyone offer some suggestions?
Thank you
Leila

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