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rfunctionplotlapply

How to loop over `. . .` in an R function

I have a function called foo(). The arguments are ....

But I want loop over the individual arguments in .... For example, if user inputs col = c(2,3), I want the first round of lapply() to use col = 2 and the second round of lapply() to use col = 3 and so on.

Is this possible in R?

Reproducible R code:

foo <- function(...){
  
  x <- list(...)
  n_plots <- lengths(x)[1]
    
  par(mfrow = n2mfrow(n_plots))
  
  lapply(1:n_plots, \(i) plot(1:10, ...))
  
}
# EXAMPLE OF USE:
foo(col = 2:3, pch = c(19,21))
Solution

  • This is a little convoluted (uses ... twice) but seems to do the trick, for an arbitrary number of arguments:

    foo <- function(...){
  L <- list(...)
  n_plots <- lengths(L)[1]  
  par(mfrow = n2mfrow(n_plots))
  ff <- function(...) {
     args <- c(list(x = 1:10), list(...))
     do.call(plot, args)
  }
  Map(ff, ...)
}

    foo(col = 2:3, pch = c(19,21), cex = 2:3)