CODEWITHSUNDEEP
rscopenested
Midnighter
Midnighter

Reputation: 3881

Passing on a function from parameter into a nested function

I a nutshell I would like to run the following minimal piece of code:

library(plyr)

surround = function(my.df, my.var, my.val, my.method) {
    ddply(my.df, my.var, summarize, value = my.method(as.name(my.val)))
}

my.df = data.frame(group = rep(letters[1:4], times = 25),
                   x = rnorm(100))

surround(my.df, "group", "x", mean)

However, this leads to Error: could not find function "my.method". I do realize that this is a scoping issue and I should be using eval or substitute but I can't figure it out.

Upvotes: 3

Views: 50

Answers (1)

drmariod
drmariod

Reputation: 11762

If you use a customised function instead of summarise, it would work.

surround <- function(my.df, my.var, my.val, my.method) {
  ddply(my.df, my.var, function(x) c(value = my.method(x[[my.val]])))
}

my.df <- data.frame(group=rep(letters[1:4], times=25),
                   x=rnorm(100))

surround(my.df, "group", "x", mean)

Upvotes: 4

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