Creating a data partition using caret and data.table

Question

I have a data.table in R which I want to use with caret package

set.seed(42)
trainingRows<-createDataPartition(DT$variable, p=0.75, list=FALSE)
head(train         


        

Answer 1

The reason is that createDataPartition produces integer vector with two dimensions where the second could be losslessly dropped.
You can simply reduce dimension of trainingRows using below:

DT[trainingRows[,1]]

The c() function from Bruce Pucci's answer will reduce dimension too.

This minor difference vs. data.frame was spotted long time ago and recently I've made PR #1275 to fill that gap.