R: Function as argument of another function

Question

I have written the R function myplot() which draws a curve corresponding to the supplied function FUN over the interval [-10, 10].

myplot <- function(FUN)
{
  curve(FUN(x), xlim = c(-10, 10))
}

For example

myplot(FUN = dnorm)

gives

How can I add arguments to FUN? For example, let's say I want to plot the normal density with mean 5.

Following @akrun's comment, I can do something like that:

myplot <- function(FUN, ...)
{
  args <- list(...)
  curve(FUN(x, unlist(args)), xlim = c(-10, 10))
}
myplot(dnorm, mean = 5)

But then

   > myplot(FUN = dnorm)
    Error in FUN(x, unlist(args)) : 
      Argument non numérique pour une fonction mathématique

Also, myplot(FUN = dnorm, mean = 5, sd = 2) does not give the expected picture...

Try dots <- list(...); curve(FUN(x, unlist(dots)), xlim = c(-10, 10)) — akrun
– akrun, Commented Feb 3, 2016 at 7:44
@akrun: Thank you! I have edited my post with further questions. Thank you again. — user7064
– user7064, Commented Feb 3, 2016 at 8:26

baptiste · Accepted Answer · 2016-02-03 08:54:08Z

2

Your original function works fine (but your original example had a typo)

myplot <- function(FUN, ...)
{
    curve(FUN(x, ...), xlim = c(-10, 10))
}

myplot(dnorm)
myplot(dnorm, mean = 5)
myplot(dnorm, mean = 5, sd=2)

all seem to work.

answered Feb 3, 2016 at 8:54

baptiste

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