Dear All, Zelig 4 no longer seems to handle predict() and fitted() as it used to, and as other R packages do. In short, given a zelig output object (say "zelig.reg"), it seems that it is necessary to invoke predict and/fitted on zelig.reg$result or zelig.reg[[1]] , and not on zelig.reg. And the behavior of functions is not consistent across different models, at least not across "ls" and "logit". A self contained example follows below. 1 - Can the default method for these functions be changed to behave as before (i.e. to accept predict(zelig.reg) and fitted(zelig.reg)? 2 - Can the behavior of predict() and fitted() be made consistent across models? #I'm running: #R version 3.0.0 (2013-04-03) #Platform: x86_64-apple-darwin10.8.0 (64-bit) #Running Zelig_4.1-3 data(npk, package="MASS") #load data ### Extracting fitted and predicted values from linear and logit regressions *not* using Zelig, all this works well: lm.reg <- lm(yield~N+P+K, data=npk) predict(lm.reg) fitted(lm.reg) logit.reg <- glm(N~yield+P, data=npk, family=binomial(link="logit")) predict(logit.reg) fitted(logit.reg) ### Extracting fitted and predcited values from linear and logit regressions using Zelig lm.zelig <- zelig(yield~N+P+K, data=npk,model="ls",cite=F) predict(lm.zelig) # does not work predict(lm.zelig[[1]]) #this "sort"of works, but spits back only 10 observations predict(lm.zelig$result) #this does not work in "ls", but does work below in "logit" predict(lm.zelig$result,newdata=lm.zelig$data) #this seems to work, but is not convenient... fitted(lm.zelig) # does not work, but in the linear case does not matter fitted(lm.zelig$result,newdata=lm.zelig$data) #this seems to work, but is not convenient... logit.zelig <- zelig(N~yield+P, data=npk, model="logit",cite=F) predict(logit.zelig) # does not work predict(logit.zelig$result) #this works, but is inconvenient predict(logit.zelig$result,newdata=logit.zelig$data) fitted(logit.zelig$result) #this seems to work in "logit", but does not work in "lm" Thank you, cz Cesar Zucco Jr. Assistant Professor Political Science Department Rutgers, The State University of New Jersey http://fas-polisci.rutgers.edu/zucco/