[R] Putting a loop in a function

Berend Hasselman bhh at xs4all.nl
Sat Apr 2 09:51:49 CEST 2011

Ben Hunter wrote:
> I'm stuck here. The following code works great if I just use it on the
> command line in a 'for' loop. Once I try to define it as a function as
> seen
> below, I get bad results. I'm trying to return a vector of column indices
> based on a short string that is contained in a selection (length of about
> 70) of long column names that changes from time to time. Is there an
> existing function that will do this for me? The more I think about this
> problem, the more I feel there has to be a function out there. I've not
> found it.
> ind <- function(col, string, vector){  # this is really the problem. I
> don't
> feel like I'm declaring these arguments properly.
>   indices <- vector(mode = 'numeric') # I am not entirely confident
> that
> this use is necessary. Is indices <- c() okay?
>   for (i in 1:length(col)){
>     num <- regexpr(str, col[i])
>     if (num != -1){
>          indices <- c(vector, i) # I've also had success with indices
> <-
> append(indices, i)
>   }
> }
> indices
> }
> ind(d[,'Column.I.want'], 'string', 'output.vector')
> Am I wrong here? I've read that the last statement in the function is what
> it will return, and what I want is a vector of integers.

It is not clear what you want. Give a simple example with input and desired
About your function:

- what's the purpose of the  argument. It isn't being used in your function.
- what is the  argument? Character? Object? in the function body vector is
used as a built-in function.


View this message in context: http://r.789695.n4.nabble.com/Putting-a-loop-in-a-function-tp3421439p3421768.html
Sent from the R help mailing list archive at Nabble.com.

More information about the R-help mailing list