Ok, here is the code and what happens: z.out <- zelig(civtotw2 ~ treat + civtotw1 + dcode1 + dcode3 + dcode4 + dcode5 + dcode6 + dcode7 + dcode8 + dcode9 + dcode10 + dcode11 + dcode12 + dcode13 + dcode14 + dcode15 + dcode16, weights="weights", data = mi(ds1, ds2, ds3, ds4, ds5), model = "ls", by = "civw1_q") #this ran successfully; note that the "civw1_q" factor is an ordinal four-point scale x.untreat <- setx(z.out, treat = 0) #this also ran successfully untreat.out <- sim(z.out, x = x.untreat) #this failed; here is the traceback: 9: stop("incompatible arguments") 8: mvrnorm(num, mu = coef(object), Sigma = vcov(object)) 7: param.lm(object[[i]], num = numM, bootstrap = bootstrap) 6: param(object[[i]], num = numM, bootstrap = bootstrap) 5: MIsimulation(object, num, prev, bootstrap, bootfn = bootfn, x = x, x1 = x1, ...) 4: sim.setx.MI(object[[i]], x = x[[i]], x1 = x1[[i]], num = numN, bootstrap = bootstrap, ...) 3: sim(object[[i]], x = x[[i]], x1 = x1[[i]], num = numN, bootstrap = bootstrap, ...) 2: sim.setx.strata(z.out, x = x.untreat) 1: sim(z.out, x = x.untreat) I get the same problem even if I don't weight the data. Another complication (or bit of evidence) is after I ran the above, I ran a piece of code that should work. It is the same model, onyl without the "by" command. The model runs fine, but when I get to "setx" I get this: Error in value[[jj]][ri] <- if (is.factor(xij)) as.vector(xij) else xij : nothing to replace with 4: rbind(deparse.level, ...) 3: rbind(dta, tmp) 2: setx.MI(z.out, treat = 0) 1: setx(z.out, treat = 0) If I close R and rerun the above, it works. Thoughts? Thanks! -c On Feb 13, 2008 2:03 PM, Olivia Lau &lt;olau(a)fas.harvard.edu&gt; wrote: > Casey, after the sim command (when you get the error), > > can you tell me the output you get when you do: > > > ? > > Also, try it without weights. Thx, O > > > > On Feb 13, 2008 11:05 AM, Casey Klofstad &lt;klofstad(a)gmail.com&gt; wrote: > >> Yeah, the demo works for me too. >> >> Here is what I am trying to run: >> >> #START CODE >> >> z.out <- zelig(civtotw2 ~ treat + civtotw1 + dcode1 + dcode3 + dcode4 >> + dcode5 + dcode6 + dcode7 + dcode8 + dcode9 + dcode10 + dcode11 + >> dcode12 + dcode13 + dcode14 + dcode15 + dcode16, weights="weights", >> data = mi(ds1, ds2, ds3, ds4, ds5), model = "ls", by = "civw1_q") >> >> x.untreat <- setx(z.out, treat = 0) >> >> x.treat <- setx(z.out, treat = 1) >> >> #note: the code appears to work fine until I get to the "sim" stage; >> that is where I get the error "Error in mvrnorm(num, mu = >> >> coef(object), #Sigma = vcov(object)) : incompatible arguments" >> >> untreat.out <- sim(z.out, x = x.untreat) >> >> treat.out <- sim(z.out, x = x.treat) >> >> FD.out <-sim(z.out, x = x.untreat, x1 = x.treat) >> >> #END CODE >> >> I'm sure I'm missing something obvious here, so thanks very much for >> your indulgence. >> >> Best, >> >> -c >> >> >> >> >> On Feb 13, 2008 10:56 AM, Kosuke Imai &lt;kimai(a)princeton.edu&gt; wrote: >>> demo(strata) works for us and so maybe you can send us the code so that > we >>> can see what the problem is? >>> >>> Thanks, >>> Kosuke >>> >>> >>> On Wed, 13 Feb 2008, Casey Klofstad wrote: >>> >>>> I'm using simple OLS. Also, I just updated from 3.0-6 to 3.1-0. That >>>> does not appear to fix the issue. >>>> >>>> Is it just the case that I can't run "sim" on a series of models that >>>> were generated with the "by" command? Or am I missing something here? >>>> >>>> Thanks much, >>>> >>>> -c >>>> >>>> On Feb 12, 2008 11:07 PM, Kosuke Imai &lt;kimai(a)princeton.edu&gt; wrote: >>>>> Which model are you using? Also, did you try the latest release? >>>>> >>>>> Kosuke >>>>> >>>>> >>>>> On Tue, 12 Feb 2008, Casey Klofstad wrote: >>>>> >>>>>> I am able to estimate my model using the "by" command in zelig to > run >>>>>> a model n times for n different values of a variable of interests. I >>>>>> am also able to then run "setx" without any errors. >>>>>> >>>>>> The problem comes when I try to run "sim." I get the error: "Error > in >>>>>> mvrnorm(num, mu = coef(object), Sigma = vcov(object)) : incompatible >>>>>> arguments." >>>>>> >>>>>> Maybe I am missing something obvious here. Thoughts? >>>>>> >>>>>> Thanks much! >>>>>> >>>>>> -c >>>>>> >>>>>> >>>>> >>>> >>>> >>>> >>>> >>> >> >> >> >> >> >> >> -- >> Casey A. Klofstad >> University of Miami >> Department of Political Science >> Coral Gables, FL >> >> klofstad(a)gmail.com >> http://moya.bus.miami.edu/~cklofstad >> > >