[R] How to append to a list dynamically?

[Linlin Yan]

Function parameters in R are passed by value, not by reference. In
order to resolve it, just remove "clusters" from the parameter list,
and use "clusters[i] <<- ..." to change the value of global variable.

On Wed, Jun 17, 2009 at 7:52 PM, Nick Angelou<nikolay12 at yahoo.com> wrote:
>
> Hi,
>
> I have a problem with dynamic appending to a list. Here is the list
> variable:
>
>
> clusters <- vector("list", 0)
>
>
> I extended in the function below:
>
>
> cluster <- function (pair, clusters)
> {
>  found <- FALSE
>  for (i in length(clusters))
>  {
>    if (length(intersect(pair, clusters[i])) > 0)
>    {
>     clusters[i] <- union(clusters[i], pair)
>     found <- TRUE
>    }
>  }
>  if (!found)
>  {
>   clusters <- list(clusters, as.vector(pair))
>  }
> }
>
>
> The function is executed in a loop:
>
>
> for (i in 1:nrow(adjMatrix))
> {
> for (j in 1:nrow(adjMatrix))
> {
>  if ((i != j) && adjMatrix[i,j] >0) # the matrix element has to be non-zero
> in order to be clustered
>  {
>    cat(rownames(adjMatrix)[i], colnames(adjMatrix)[j], "\n")
>    cluster(as.vector(c(rownames(adjMatrix)[i], colnames(adjMatrix)[j])),
> clusters)
>  }
> }
> }
>
>
> But the list variable remains empty (i.e. length(clusters) = 0) even though
> it should not. Somehow the dynamic extension of the list does not work in
> this case. Any suggestions?
>
> Best regards,
>
> Nick
> --
> View this message in context: http://www.nabble.com/How-to-append-to-a-list-dynamically--tp24071794p24071794.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>