Question

I need to reduce the consecutive NA’s in a vector to a single NA, without touching the other values.
So, for example, given a vector like this:

NA NA  8  7 NA NA NA NA NA  3  3 NA -1  4

what I need to get, is the following result:

NA  8  7 NA  3  3 NA -1  4

Currently, I’m using the following function:

reduceConsecutiveNA2One <- function(vect){
  enc <- rle(is.na(vect))

  # helper func
  tmpFun <- function(i){
    if(enc$values[i]){
      data.frame(L=c(enc$lengths[i]-1, 1), V=c(TRUE,FALSE))
    }else{
      data.frame(L=enc$lengths[i], V=enc$values[i])
    }
  }

  Df <- do.call(rbind.data.frame,lapply(1:length(enc$lengths),FUN=tmpFun))

  return(vect[rep.int(!Df$V,Df$L)])
}

and it seems to work fine, but probably there’s a simpler/faster way to accomplish this task.

Any suggestions ?

Thanks in advance.

Answer 1

Here’s one idea:

x <- c(NA, NA,8,7,NA, NA, NA, NA, NA, 3, 3, NA, -1,  4)

x[!(is.na(x) & diff(c(FALSE, is.na(x)))==0)]
# [1] NA  8  7 NA  3  3 NA -1  4

## It also works for length-one vectors
x <- NA
x[!(is.na(x) & diff(c(FALSE, is.na(x)))==0)]
# [1] NA