Zelig December 2013

zelig@lists.gking.harvard.edu

8 participants
5 discussions

by Edward Downie

I'm unable to locate this file: Rstatistics.zip I'm told I need in: http://projects.iq.harvard.edu/rtc/r-stats to run Instructor - Ista Zahn's workshop: R Regression Models I gather Rstatistics.zip contains the NH11 data Thanks for the help! -Edward Downie

10 years, 4 months

Obtaining risk ratio from simulation output

by Chris Compton

Dear List Members, In a previous version of Zelig (unsure of version number) it was possible to extract both the first difference and risk ratio from the summary () function, as in the below steps Model: z.out.1 <- zelig(bhbahi~treatment+agecat+breedcat+herd_initials, model = "logit", data = dat) Simulated quantities of interest: x.0 <- setx(z.out.1, treatment = "Control") x.1 <- setx(z.out.1, treatment = "Treatment") s.out.2 <- sim(z.out.1, x = x.0, x1 = x.1) Summary of first difference and risk ratio summary(s.out.2) However, changes have removed risk ratio from the quantities of interest and summary () output. The $qi now contains only: > names(s.out.2$qi) [1] "Expected Values: E(Y|X)" "Expected Values: E(Y|X1)" [3] "Predicted Values: Y|X" "Predicted Values: Y|X1" [5] "First Differences: E(Y|X1) - E(Y|X)" My question is- is there a convenient way to obtain risk ratios and confidence intervals with the new version? I am running Zelig version 4.2-1 on R version 3.0.2 on a Windows 7 platform Thanks for any help. Chris Compton

10 years, 4 months

Question on: "an error fitting this statistical model."

by Vijayaraghavan, Rajesh

Dear Zelig users, Greetings! I am relatively new to Zelig and R. But have a question when I run a linear least square model: output <- zelig(y ~ x, model ="ls"). When I run using my data, I get the following warning message. In value[[3L]](cond) : There was an error fitting this statistical model. I tried to look around to see what the issue could be but didn't have much luck. I tried to see if it is a data issue and played around with lalonde to try replicating so that I could forward to you. data(lalonde) z.out <- zelig(re78 ~ treat + age + educ + black + hispan + married + re74 + re75, data = lalonde, model = "ls") output does not have any warnings. However if I add "nodegr" covariate, I get the warning message again. z.out <- zelig(re78 ~ treat + age + educ + black + hispan + nodegr + married + re74 + re75, data = lalonde, model = "ls") Any advice on what should I do to fix would be deeply appreciated. If you think it may be addressed elsewhere, please let me know. Best , Rajesh

10 years, 4 months

(no subject)

by elham haem

Hi I have a data set with 256 infants. only 10 out of 256 were low birth weight(y bar=10/256). I want to evaluate low birth weight risk factors by relogit model. when I run my code I receive an error. I have attached my data set and my code. please help me to fit this model. Thanks in advance. Elham

10 years, 4 months

2 Errors: No log-link for Gamma Regressions and Setx not working

by Rogério Barbosa

Hi, I'm facing two difficulties... *The first one:* I'm trying to estimate a survey weighted Gamma Regression with log link, but I found out that Zelig inform just the results for the inverse link. Adding "family=Gamma(link=log)" does not work. See the example below: install.packages("Zelig") require(Zelig) #Loading data data(api, package = "survey") # Gamma inverse z.inverse <- zelig(api00 ~ meals + yr.rnd + as.factor(awards), model = "gamma.survey", weights = ~pw, data = apistrat, family=Gamma(link=inverse)) # Gamma log z.log <- zelig(api00 ~ meals + yr.rnd + as.factor(awards), model = "gamma.survey", weights = ~pw, data = apistrat, family=Gamma(link=log)) #comparison coefficients(z.inverse) == coefficients(z.log) *#inverse-link and log-link coefficients must be different, but they are not* * (Intercept) meals yr.rndYes as.factor(awards)Yes * * TRUE TRUE TRUE TRUE * ######################### g.inverse <- glm(api00 ~ meals + yr.rnd + as.factor(awards), weights = pw, data = apistrat, family=Gamma(link="inverse")) g.log <- glm(api00 ~ meals + yr.rnd + as.factor(awards), weights = pw, data = apistrat, family=Gamma(link="log")) #comparison coefficients(g.inverse) == coefficients(g.log) *#glm brings the correct results* * (Intercept) meals yr.rndYes as.factor(awards)Yes * * FALSE FALSE FALSE FALSE * *The second one:* I'm not getting the output for setx in any model! Not even for "model='ls' " # In the example above: meals_seq=seq(from=1,to=30,by=1) setx(z.inverse, meals=meals_seq) *Call:* *NULL* *Model name = * *Formula = NULL* *Complete data.frame:* *NULL* *Model Matrix (Design Matrix):* *NULL* I'm using R 3.0.2 and Zelig 4.2-1. Rolling back to Zelig 3.5.4 is not worth in this case... setx works fine in that version, but "gamma.survey" does not. thanks in advance, Rogério J Barbosa Universidade de São Paulo, Brazil

10 years, 5 months

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Zelig December 2013