I'm running a multinomial logit in R using the Zelig package. However I get the following error. HELP anes96two <- zelig(trade962a ~ age962 + education962 + personal962 + economy962 + partisan962 + employment962 + union962 + home962 + market962 + race962 + income962, model="mlogit", data=data96) #Error in attr(tt, "depFactors")$depFactorVar : # $ operator is invalid for atomic vectors