[R] for loop question

[Uwe Ligges]

"HEUMANN,JOHN (A-Loveland,ex1)" wrote:
> 
> In the windows version of R (1.3.0) is the following a bug, a
> known problem, or expected behavior:
> 
>  > for (i in 1:2) {
>  + for (j in i+1:3) {
>  + print(j)
>  + }
>  + }
>  [1] 2
>  [1] 3
>  [1] 4      ????
>  [1] 3
>  [1] 4      ????
>  [1] 5      ????

Looks extremly as expected:

  # outer loop i=1
# [1] 2     i=1, j=i+1
# [1] 3     i=1, j=i+2
# [1] 4     i=1, j=i+3
  # outer loop i=2
# [1] 3     i=2, j=i+1
# [1] 4     i=2, j=i+2
# [1] 5     i=2, j=i+3


> Conversely, the following behaves as expected:
> 
>  > for (i in 1:2) {
>  + k <- i+1
>  + for (j in k:3) {
>  + print(j)
>  + }
>  + }
>  [1] 2
>  [1] 3
>  [1] 3


What you mean is (the braces!!!):

 for (i in 1:2) {
  for (j in (i+1):3)
   print(j)
 }

Have a look at this (no spaces are here asn intentional negative
example):
1+1:3 # the sequence is evaluated at first!


Another way to do your calculation:

i <- 1:2
j <- 3
lapply(i, function(x) seq(x+1,j))


Uwe Ligges
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