Data frame vs matrix quirk: Hinky error message?

AdvisoRs:

Is the following a bug, feature, hinky error message, or dumb Bert?

mtest <- matrix(1:12,nr=4)
dftest <- data.frame(mtest)
ix <- cbind(1:2,2:3)
mtest[ix] <- NA
mtest

[,1] [,2] [,3]
[1,]    1   NA    9
[2,]    2    6   NA
[3,]    3    7   11
[4,]    4    8   12

## But ...

dftest[ix] <- NA

Error in `[<-.data.frame`(`*tmp*`, ix, value = NA) :
  only logical matrix subscripts are allowed in replacement

Obviously, I was expecting matrix indexing for replacement to work
similarly in both cases; however, I can see why it would be
problematic for data frames (mixed types), but was a bit nonplussed by
the error message, which seems hinky to me.

Cheers,
Bert

Bert Gunter
Genentech Nonclinical Biostatistics

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