On 6/30/2010 1:14 AM, Daniel Chen wrote:
> Hi,
>
> I am a long time SPSS user but new to R, so please bear with me if my
> questions seem to be too basic for you guys.
>
> I am trying to figure out how to analyze survey data using logistic
> regression with multiple imputation.
>
> I have a survey data of about 200,000 cases and I am trying to predict the
> odds ratio of a dependent variable using 6 categorical independent variables
> (dummy-coded). Approximatively 10% of the cases (~20,000) have missing data
> in one or more of the independent variables. The percentage of missing
> ranges from 0.01% to 10% for the independent variables.
>
> My current thinking is to conduct a logistic regression with multiple
> imputation, but I don't know how to do it in R. I searched the web but
> couldn't find instructions or examples on how to do this. Since SPSS is
> hopeless with missing data, I have to learn to do this in R. I am new to R,
> so I would really appreciate if someone can show me some examples or tell me
> where to find resources.
Here is an example using the Amelia package to generate imputations
and the mitools and mix packages to make the pooled inferences.
titanic <-
read.table("http://lib.stat.cmu.edu/S/Harrell/data/ascii/titanic.txt";,
sep=',', header=TRUE)
set.seed(4321)
titanic$sex[sample(nrow(titanic), 10)] <- NA
titanic$pclass[sample(nrow(titanic), 10)] <- NA
titanic$survived[sample(nrow(titanic), 10)] <- NA
library(Amelia) # generate multiple imputations
library(mitools) # for MIextract()
library(mix) # for mi.inference()
titanic.amelia <- amelia(subset(titanic,
select=c('survived','pclass','sex','age')),
m=10, noms=c('survived','pclass','sex'),
emburn=c(500,500))
allimplogreg <- lapply(titanic.amelia$imputations,
function(x){glm(survived ~ pclass + sex + age, family=binomial, data = x)})
mice.betas.glm <- MIextract(allimplogreg, fun=function(x){coef(x)})
mice.se.glm <- MIextract(allimplogreg, fun=function(x){sqrt(diag(vcov(x)))})
as.data.frame(mi.inference(mice.betas.glm, mice.se.glm))
# Or using only mitools for pooled inference
betas <- MIextract(allimplogreg, fun=coef)
vars <- MIextract(allimplogreg, fun=vcov)
summary(MIcombine(betas,vars))
> Thank you!
>
> Daniel
>
> [[alternative HTML version deleted]]
>
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