问题
I want to perform multigroup SEM on imputed data using the R packages mice and semTools, specifically the runMI function that calls Lavaan.
I am able to do so when imputing the entire dataset at once, but whilst trawling through stackoverflow/stackexchange I have come across the recommendation to impute data separately for each level of a grouping variable (e.g. men, women), so that the features of each group are preserved (e.g. https://stats.stackexchange.com/questions/149053/questions-on-multiple-imputation-with-mice-for-a-multigroup-sem-analysis-inclu). However, I've not been able to find any references to support this course.
My question is both conceptual and practical -
1) Is splitting the dataset by group prior to imputing the correct course? Could anyone point me towards references advising this?
2) If so, how can I combine the datasets imputed by group using mice together, whilst still retaining multiple imputed datasets in a list of dataframes of the mids class? I have attempted to do so, but end up with an integer
set.seed(12345)
HSMiss <- HolzingerSwineford1939[ , paste("x", 1:9, sep = "")]
HSMiss$x5 <- ifelse(HSMiss$x1 <= quantile(HSMiss$x1, .3), NA, HSMiss$x5)
HSMiss$x9 <- ifelse(is.na(HSMiss$x5), NA, HSMiss$x9)
HSMiss$school <- HolzingerSwineford1939$school
HS.model <- '
visual =~ x1 + a*x2 + b*x3
textual =~ x4 + x5 + x6
x7 ~ textual + visual + x9
'
group1 <- subset(HSMiss, school =='Pasteur')
group2 <- subset(HSMiss, school =='Grant-White')
imputed.group1 <- mice(group1, m = 3, seed = 12345)
imputed.group2 <- mice(group2, m = 3, seed = 12345)
#attempted merging:
imputed.both <- nrow(complete(rbind(imputed.group1, imputed.group2)))
I would be incredibly grateful if anyone can offer me some help. As you can tell, I am very much still learning about R and imputation, so apologies if this is a stupid question - however, I couldn't find anything regarding this specific query elsewhere.
回答1:
You are getting just an integer when mergin because you are calling nrow(). Remove that call and you'll get a merged data frame.
imputed.both <- complete(rbind(imputed.group1, imputed.group2))
In case you find yourself with datasets that have multiple groups, you can something like the following to simplify this task.
imputed.groups <- lapply(split(HSMiss, HSMiss$school), function(x) {
complete(mice(x, m = 3, seed = 12345))
})
imputed.both <- do.call(args = imputed.groups, what = rbind)
About how appropiate is this approach for imputing, that's probably a question better suited for Cross Validated.
来源：https://stackoverflow.com/questions/48770037/multiple-imputation-and-multigroup-sem-in-r