Function for adding a column in a data.frame if it is not already in it

Asked Dec 06 '17 at 15:02

Active Dec 06 '17 at 15:08

Viewed 19 times

Greeting,

I am currently trying to set up a function to add a column to a dataframe if it doesn't already exists. Let's say columns is a vector of names I want in my dataframe. Here is what I have so far... For some reasons it adds an "i" column and that's it. I think the problem should come from the definition of i in the function, but I've tried several changes and that's still not working. Any clue ? Thanks a lot!

add_columns <- function(x){
'%!in%' <- function(u,v)!('%in%'(u,v))
for(i in columns){
if(i %!in% colnames(x)) {
  x$"i" <-100
  return(x)
  }
 }
}

edited Dec 06 '17 at 15:08

asked Dec 06 '17 at 15:02

Pierre-Jean Cottalorda

"a function to add a function to a dataframe" - typo? – talat Dec 06 '17 at 15:06
1

Can't use strings with `$`, use `[[` instead. `x[[i]] <- 100`. Also, as soon as `return()` is called, the function ends. You want the `return()` to be *after* the `for` loop, not inside it. – Gregor Thomas Dec 06 '17 at 15:07
Thanks a lot Gregor, that's working perfectly! – Pierre-Jean Cottalorda Dec 06 '17 at 15:15

Function for adding a column in a data.frame if it is not already in it

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