[R] For loop into a vectorized form?

[David Winsemius]

On Jan 29, 2010, at 9:31 AM, johannes rara wrote:

> How to vectorize this for loop and how can I assign result to vector
> instead of using print function?

 > as.vector( sapply(mylist$a, function(x)
                            sapply(mylist$b, function (y)
                                        { c(x,  y, mylist[[3]]) }
             ) ) )

  [1] "a" "A" "1" "2" "3" "a" "B" "1" "2" "3" "a" "C" "1" "2" "3" "b"  
"A" "1" "2" "3" "b" "B" "1" "2"
[25] "3" "b" "C" "1" "2" "3" "c" "A" "1" "2" "3" "c" "B" "1" "2" "3"  
"c" "C" "1" "2" "3"

You did say you wanted a vector, right?

-- 
David.

>
> mylist <- list(a = letters[1:3], b = LETTERS[1:3], c = c("1", "2",  
> "3"))
>
> for (i in seq_along(mylist[[1]])) {
>     for (j in seq_along(mylist[[2]])) {
>        print(mylist[[1]][i])
>        print(mylist[[2]][j])
>        print(mylist[[3]])
>     }
> }
>
>
> Run version:
>
>> mylist <- list(a = letters[1:3], b = LETTERS[1:3], c = c("1", "2",  
>> "3"))
>> mylist
> $a
> [1] "a" "b" "c"
>
> $b
> [1] "A" "B" "C"
>
> $c
> [1] "1" "2" "3"
>
>> for (i in seq_along(mylist[[1]])) {
> +      for (j in seq_along(mylist[[2]])) {
> +         print(mylist[[1]][i])
> +         print(mylist[[2]][j])
> +         print(mylist[[3]])
> +      }
> + }
> [1] "a"
> [1] "A"
> [1] "1" "2" "3"
> [1] "a"
> [1] "B"
> [1] "1" "2" "3"
> [1] "a"
> [1] "C"
> [1] "1" "2" "3"
> [1] "b"
> [1] "A"
> [1] "1" "2" "3"
> [1] "b"
> [1] "B"
> [1] "1" "2" "3"
> [1] "b"
> [1] "C"
> [1] "1" "2" "3"
> [1] "c"
> [1] "A"
> [1] "1" "2" "3"
> [1] "c"
> [1] "B"
> [1] "1" "2" "3"
> [1] "c"
> [1] "C"
> [1] "1" "2" "3"
>>
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT