I have some - for me - unresolvable troubles with glm. First call: glm(n~.,data=mDat,family=poisson,control = list(trace = TRUE)) Error in 1:control$maxit : NA/NaN argument Second call: glm(n~.,data=mDat,family=poisson,control = list(trace = TRUE,maxit=1)) Deviance = 23.48436 Iterations - 1 Error in if (abs(dev - devold)/(0.1 + abs(dev)) < control$epsilon) { : argument is of length zero Some of the response counts are zero - so third call: glm(n~.,data=mDat[mDat$n>0,],family=poisson,control = list(trace = TRUE,maxit=1)) Deviance = 17.63633 Iterations - 1 Error in if (abs(dev - devold)/(0.1 + abs(dev)) < control$epsilon) { : argument is of length zero Anyone having a clue to this problem? Best wishes svante