Error: missing value where True/False

Question

I am trying to delete all values in a list that have the tag ".dsw". My list is a list of files using the function list.files. This is my code:

for (file in GRef) {
  if (strsplit(file, "[.]")[[1]][3] == "dsw") {
     #GRef=GRef[-file]
    for(n in 1:length(GRef)){
      if (GRef[n] == file){
        GRef=GRef[-n]
      }
    }
  }
}

Where GRef is the list of file names. I get the error listed above, but I dont understand why. I have looked at this post: Error .. missing value where TRUE/FALSE needed, but I dont think it is the same thing.

Please provide more detail: show a sample of the content in GRef. — Abdou
you probaby have an NA in the first outer if statement. Put a print call right before the if printing the left hand side of the equality. — Adam
It is likely the result of a file that only has a single . in it, which means indexing it at 3 would be out of bounds — Adam

MrFlick MrFlick · Accepted Answer · 2016-07-27T15:25:26

You shouldn't attempt to to modify a vector while you are looping over it. The problem is your are removing items you are then trying to extract later which is causing the missing values. It's better to identify all the items you want remove first, then remove them. For example

GRef <- c("a.file.dsw", "b.file.txt", "c.file.gif", "d.file.dsw")
exts <- sapply(strsplit(GRef, "[.]"), `[`, 3)
GRef <- GRef[exts!="dsw"]

Error: missing value where True/False

1 Answers