Why does MICE fail to impute multilevel data with 2l.norm and 2l.pan?

Question

Why does MICE fail to impute multilevel data with 2l.norm and 2l.pan in this situation ?

Here is a reproducible example:

require(foreign)
require(mice)
require(pan)

dt.fail <- read.csv("http://goo.gl/pg8um")
dt.fail$X <- NULL

dt.fail$out <- as.factor(dt.fail$out )
dt.fail$grp<- as.factor(dt.fail$grp)
dt.fail$v1<- as.factor(dt.fail$v1)
dt.fail$v2<- as.factor(dt.fail$v2)
dt.fail$v3 <- as.factor(dt.fail$v3)
dt.fail$v7<- as.factor(dt.fail$v7)
dt.fail$v8 <- as.factor(dt.fail$v8)
dt.fail$v9 <- as.factor(dt.fail$v9)
dt.fail$v11 <- as.factor(dt.fail$v11)
dt.fail$v12 <- as.factor(dt.fail$v12)

dt.fail <- dt.fail[!is.na(dt.fail$grp),]

PredMatrix <- quickpred(dt.fail)
PredMatrix['CTP',] <- c(1,-2,0,0,0,0,0,0,0,0,1,0,1,1,0,2)


impute = mice(
data=dt.fail, 
m = 1, 
maxit = 1,
    imputationMethod = c(
        "logreg",   # out
    "",     # grp   ----> cluster grouping factor
        "pmm",  # v1
        "polyreg",  # v2
        "logreg",   # v3
        "pmm",  # v4
        "logreg",   # v5
        "logreg",   # v6
    "polyreg",  # v7 
        "polyreg",  # v8 
        "polyreg",  # v9 
        "polyreg",  # v10
        "",     # v11 ----> complete
        "",     # v12 ----> complete
        "2l.pan",   # CTP ----> multilevel imputation
        ""),        # const ----> needed for multilevel impuitation
predictorMatrix = PredMatrix, seed = 101
)

This produces the following error:

Error in order(dfr$group) : argument 1 is not a vector

Using the 2l.norm method, it produces the following error:

Error in factor(x[, type == (-2)], labels = 1:n.class) :  invalid labels; length 20592 should be 1 or 2

Using pmm there is no error

Answer 1

This is a bug in mice 2.15 and before. mice.impute.2l.norm() and mice.impute.2l.pan() will fail if the cluster variable is a factor. Use as.integer(dfr$group) as a temporary fix in your data. I will address the issue in a future release. Thanks for your persistence.