An error is issued when merging three (or more) data.tables with rbind and there is an empty data.table between two non-empty data.tables:
> require(data.table)
Loading required package: data.table
data.table 1.9.2 For help type: help("data.table")
> DT <- data.table(x=c(1,2,3))
> rbind(DT, data.table(), DT)
Error in setcolorder(tt, chmatch(match.names, make.names(original.names[[x]], (from <text>#1) :
Column numbers in neworder out of bounds: NA
This does not happen if the empty data.table is in the end:
> rbind(DT, DT, data.table())
x
1: 1
2: 2
3: 3
4: 1
5: 2
6: 3
But some other error happens when the empty data.table is in the beginning:
> rbind(data.table(), DT, DT)
Error in data.table::.rbind.data.table(...) (from <text>#1) :
Some colnames of argument 2 (x) are not present in colnames of item 1. If an argument has colnames they can be in a different order, but they must all be present. Alternatively, you can supply unnamed lists and they will then be joined by position. Or, set use.names=FALSE.
However, if we use only two arguments everything is fine:
> rbind(data.table(), DT)
x
1: 1
2: 2
3: 3
What should be the expected behavior?