Hi again (, I am the PO from my own email account) I agree that the word "basically" puts the NA issues aside. But my point is that R subsetting behavior when there are NAs in a logical index is quite tricky to say the less, and deserves the trouble of pointing it out in every place it is appropiate. As "which()" is the function I use to overcome this issue, I thought it would be good to emphasize that it solves this situation in a different way that the subsetting operation does. I am aware that it is clearly stated above in the help page though. But I still would change the expression rather than "hiding" this distinction. And the "diplomatic refinement seems even better to me.