Combine output vectors into dataframe

I wrote a function with a vector of length 3 as output which has a structure like this:

func <- function(input){
    a <- 15+input
    b <- 5+input
    c <- -5+input
    return(c(a,b,c)) 
}

and I have input values input <- seq(200,300)

I'd like to call the function 100 times (length(input)), then I'd like to calculate the output vectors for each value in input and I'd like to combine the output vectors into a dataframe.

How can I do this efficiently?

EDIT: I made a mistake. length(input) is 101 in that case.

Solution

You can do this with sapply, which gives you a 3x101 matrix, transpose it, then convert it to a data frame. If you want the colnames to be a, b, c then you can set them after:

sapply(input, func) |> # Apply `func` to every input separately
  t() |> # Transpose
  as.data.frame() # convert to data frame

This gives output:

     V1  V2  V3
1   215 205 195
2   216 206 196
3   217 207 197
4   218 208 198
5   219 209 199
6   220 210 200
7   221 211 201
8   222 212 202
9   223 213 203
10  224 214 204
...
...
...

Alternatively, if you name your return list with a, b, and c, you can get the names out:

func <- function(input){
  a <- 15+input
  b <- 5+input
  c <- -5+input
  return( c(a = a,b = b, c = c) ) # Note the names 
}

sapply(input, func) |>
  t() |>
  as.data.frame()

returns

      a   b   c
1   215 205 195
2   216 206 196
3   217 207 197
4   218 208 198
5   219 209 199
6   220 210 200
7   221 211 201
8   222 212 202
9   223 213 203
10  224 214 204
...
...
...

Finally, you can return a data frame from your function, do an lapply to apply the function to each input then bind all the rows together:

func <- function(input){
  a <- 15+input
  b <- 5+input
  c <- -5+input
  return(data.frame(a = a, b = b, c = c)) 
}

lapply(input, func) |>
  do.call(rbind, args = _)

which returns the same as above.