Search code examples
rfunctionlapply

R: lapply function - skipping the current function loop

I am using a lapply function over a list of multiple files. Is there a way in which I can skip the function on the current file without returning anything and just skip to the next file in the list of the files?

To be precise, I have an if statement that checks for a condition, and I would like to skip to the next file if the statement returns FALSE.

Solution

  • lapply will always return a list the same length as the X it is provided. You can simply set the items to something that you can later filter out.

    For example if you have the function parsefile

    parsefile <-function(x) {
  if(x>=0) {
    x
  } else {
    NULL
  }
}

    Edit: { As Florent Angly shows, you should replace NULL with NA}

    and you run it on a vector runif(10,-5,5)

    result<-lapply(runif(10,-5,5), parsefile)

    then you'll have your list filled with answers and NULLs

    You can subset out the NULLs by doing...

    result[!vapply(result, is.null, logical(1))]