Return FALSE for duplicated NA values when using the function duplicated()
You use the argument incomparables for the function duplicated like this :
> duplicated(c(NA,NA,NA,1,2,2))[1] FALSE TRUE TRUE FALSE FALSE TRUE> duplicated(c(NA,NA,NA,1,2,2),incomparables=NA)[1] FALSE FALSE FALSE FALSE FALSE TRUEIt determines the values that cannot be compared (in this case NA) and returns FALSE for those values. See also ?duplicated