Hi, I have a problem.... I need help about Generalized Estimating Equation. The response variable is "efficacy" (numeric) and the predictors are "eziology" (categoric) and "terapy" (string). After downloaded the gee from CRAN I tried to use this procedure for example: summary(gee(efficacy~eziology+terapy, id=?, data=pippo, corstr="exchangeable")) Could you send me an example of application of GEE with two variables? Thank you very much Paola Di Stefano