[R] How to pass a model formula as argument to with.mids
Erich Studerus
erich.studerus at bli.uzh.ch
Thu Sep 23 15:53:45 CEST 2010
Hello
I would like to pass a model formula as an argument to the with.mids
function from the mice package. The with.mids functon fits models to
multiply imputed data sets.
Here's a simple example
library(mice)
#Create multiple imputations on the nhanes data contained in the mice
package.
imp <- mice(nahnes)
#Fitting a linear model with each imputed data set the regular way works
fine
with(imp, lm(bmi~hyp+chl))
#Creating a formula object and than passing it as argument does not work:
form.obj <- formula(bmi~hyp+chl)
with(imp, lm(form.obj))
#The following doesn't work either
expr <-"lm(bmi~hyp+chl)"
with(imp, expr)
Looking at the definition of with.mids reveals that the second argument
is first substituted and than evaluated within each data.frame of the
multiply imputed data sets. Is there a way to pass "lm(bmi~hyp+chl)"
without having to change the definition of the with.mids function?
Thanks in advance,
Erich
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