How to assign from a function with multiple outputs? [duplicate]

Question

Is there a way to output e.g. 2 objects without using list()?

my.fun=function(vector, index)
       {
       a=fun.a(vector, index)
       b=fun.b(vector, index)
       output=list(a,b)
       }

Or to output 2 lists of objects? Considering that I could also have:

       c=fun.a(vector, index)
       d=fun.b(vector, index)

And wanted list(a,b) and another list(c,d) for the same function.

This is just a small example for what I am looking for, my function is applied to large objects and I export them as a list, however I would like to export also an intermidiate calculation. One option would be to merge all in the same list, but I would like to know if there is another solution to this.

Answer 1

You can only return one object in a function. But you have some other options. You could assign intermediate objects to the global environment (you need to be careful not to overwrite anything) or you could pass an environment to your function and assign objects to it.

Here's an example of the latter suggestion:

fun <- function(x, env) {
  env$x2 <- x^2
  x^3
}
set.seed(21)
x <- rnorm(10)
myEnv <- new.env()
fun(x, myEnv)
#  [1]  4.987021e-01  1.424421e-01  5.324742e+00 -2.054855e+00  1.061014e+01
#  [6]  8.125632e-02 -3.871369e+00 -8.171530e-01  2.559674e-04 -1.370917e-08
myEnv$x2
#  [1] 6.288699e-01 2.727464e-01 3.049292e+00 1.616296e+00 4.828521e+00
#  [6] 1.876023e-01 2.465527e+00 8.740486e-01 4.031405e-03 5.728058e-06