I have the same objection to #Rstats that I do to heavy historical tabletop wargames: too many special case exceptions.

> m = matrix(1:6, nrow=3)
> m
[,1] [,2]
[1,] 1 4
[2,] 2 5
[3,] 3 6
> a = c(1, 2)
> b = c(1)
> dim(m[a,])
[1] 2 2
> dim(m[b,])
NULL
> dim(m[b,, drop=FALSE])
[1] 1 2

@data_science