rmatchingpropensity-score-matchingcausal-inference

MatchThem and reference levels

After applying matching on multiple imputed datasets. How do I set the reference levels for categorical variables in my final model. For example how do I set the reference level for KOA as 1 instead of 0 ? Thanks

library(MatchThem)

data("osteoarthritis")

library(mice)
imputed.datasets <- mice(osteoarthritis, m = 5)

table(imputed.datasets$data$OSP)

table(imputed.datasets$data$KOA)

matched.datasets <- matchthem(OSP ~ AGE + SEX + BMI + RAC + SMK,
                              datasets = imputed.datasets,
                              approach = 'within',
                              method = 'nearest',
                              caliper = 0.05,
                              ratio = 2)

library(survey)
matched.models <- with(matched.datasets,
                       svyglm(KOA ~ OSP, family = quasibinomial()),
                       cluster = TRUE)
Solution

  • You can just make the outcome KOA == 0, e.g.,

    svyglm(KOA == 0 ~ OSP, family = quasibinomial())

    Note this doesn't really have anything to do with matching or multiple imputation.