Passing a function from a parameter to a nested function
I would like to briefly 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 understand this is a problem and I have to use eval
or substitute
, but I cannot figure it out.
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1 answer
If you use a custom function instead of summing it will 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)
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