Re: [zelig] Problem with setx after using as.factor in the regression - Matchit

15 May 2008

Do you have the latest version of Zelig? It works for me:

...
  setx(z.out1, age = 20)    (Intercept) age
as.factor(race)white
1           1  20                    1

Kosuke

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Kosuke Imai               Office: Corwin Hall 041
Assistant Professor       Phone: 609-258-6601
Department of Politics    eFax:  973-556-1929
Princeton University      Email: kimai(a)Princeton.Edu
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On Thu, 15 May 2008, Andrew Stokes wrote:

...
  Hello,

 When I run a regression using as.factor to create indicator variables from
 categorical variables, the subsequent simulation steps using setx and sim do
 not work. When I run the regression where the indicator variables were
 created beforehand, the simulation steps work. So for example, I run

 z.out<-zelig(severe_anemic ~ net_status + anc_visit + as.factor(age) +
 as.factor(wealth) + as.factor(region), model = "logit", data = my.data)

 And then I run:

 x.out0<-setx(z.out, net_status = 0)
 x.out1<-setx(z.out, net_stutus = 1)
 s.out<-sim(z.out, x=x.out0, x1=x.out1, num=1000)

 After each of the preceding lines, I receive this error:

 Error in `contrasts<-`(`*tmp*`, value = "contr.treatment") :
  contrasts can be applied only to factors with 2 or more levels

 Thanks for any advice!

 Andrew Stokes
 Institute for Health Metrics and Evaluation

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