Can't assign NA for a factor

[Zus]

When trying to assign NA to a specfic items in a factor, an error is thrown, which does not happen in base DF.

require(data.table)
DT <- data.table(x = 1:5,y = factor(c("","a","b","a", "")), z = 5:9)
DT[y==""]
DT[y=="", y := NA] # throws an error, interpreted as logical
DT[y=="",y] <- NA # throws an error

R 3.3.0 DT 1.96

[jangorecki]

It works if you provide a factor type value on RHS of :=, this can be done with as.factor(NA) or even as.integer(NA) (because factor is of integer type):

DT[y=="", y := as.factor(NA)]

But I agree to make sense to catch that automatically.

[arunsrinivasan]

It was expecting an integer (NA_integer_). But the coercion is handled on logical types as well.