Apply list of functions to list of values

Question

In reference to this question, I was trying to figure out the simplest way to apply a list of functions to a list of values. Basically, a nested lapply. For example, here we apply sd and mean to built in data set trees:

funs <- list(sd=sd, mean=mean) sapply(funs, function(x) sapply(trees, x)) 

to get:

              sd     mean Girth   3.138139 13.24839 Height  6.371813 76.00000 Volume 16.437846 30.17097 

But I was hoping to avoid the inner function and have something like:

sapply(funs, sapply, X=trees) 

which doesn't work because X matches the first sapply instead of the second. We can do it with functional::Curry:

sapply(funs, Curry(sapply, X=trees)) 

but I was hoping maybe there was a clever way to do this with positional and name matching that I'm missing.

Answer 1

Since mapply use ellipsis ... to pass vectors (atomics or lists) and not a named argument (X) as in sapply, lapply, etc ... you don't need to name the parameter X = trees if you use mapply instead of sapply :

funs <- list(sd = sd, mean = mean)  x <- sapply(funs, function(x) sapply(trees, x))  y <- sapply(funs, mapply, trees)  > y               sd     mean Girth   3.138139 13.24839 Height  6.371813 76.00000 Volume 16.437846 30.17097 > identical(x, y) [1] TRUE 

You were one letter close to get what you were looking for ! :)

Note that I used a list for funsbecause I can't create a dataframe of functions, I got an error.

> R.version.string [1] "R version 3.1.3 (2015-03-09)"