Hi everybody, I'm trying to select a model with the function step. It is a mixed generalized linear model fitted by the function glmmML. I have one random variable (id), one response variable (var) and many independent variables (x1, x2, x3..). I obtain the following error: Error in if (all(is.finite(c(n0, nnew))) && nnew != n0) stop("number of rows in use has changed: remove missing values?") : missing value where TRUE/FALSE needed But I swear that I do NOT have any NA in my database (data1). I have checked it many times even with is.na() My script is the following: model<-step(glmmML(var~1,cluster = id, family = poisson,data data1),direction=c("both"),data=data1,scope=~x1+x2+x3+x4+x5+x6+x7+x8+x9+x10) Does anybody know where the problem could be? Thank you in advance, Alba -- View this message in context: http://r.789695.n4.nabble.com/Error-with-step-and-glmmML-tp4095404p4095404.html Sent from the R help mailing list archive at Nabble.com.