> matrix(1)[[1,]]Error in matrix(1)[[1, ]] : invalid subscript type 'symbol' This is of course an incorrect use of [[, but I think the error message could be more helpful. I will guess that it is interpreting the missing value indicator as a symbol, since I get the same error message for> matrix(1)[[ quote(a=), ]]-s PS quote(a=) seems to be the easiest way to get the missing value indicator as a value. Is it by design that it returns the MVI? Or is it a missing error check?