R help - Aug 2005 - problem with for()

Dear list,
can someone tell me why this two pieces of code give me the same  
results?

 > for(i in 0:5){ sum[i] = i }
 > sum
[1] 1 2 3 4 5

 > for(i in 1:5){ sum[i] = i }
 > sum
[1] 1 2 3 4 5

shouldn't the first one be

0 1 2 3 4 5

thank you,
simone

Simone Gabbriellini <ogabbrie at tin.it> writes:
> Dear list,
> can someone tell me why this two pieces of code give me the same  
> results?
> 
>  > for(i in 0:5){ sum[i] = i }
>  > sum
> [1] 1 2 3 4 5
> 
>  > for(i in 1:5){ sum[i] = i }
>  > sum
> [1] 1 2 3 4 5
> 
> shouldn't the first one be
> 
> 0 1 2 3 4 5
No. Indexing starts at 1 in R.

Next, figure out this:
> sum=0
> for(i in 5:-5){ sum[i] = i }
> sum
[1] -5 -5 -5 -5 -4


-- 
   O__  ---- Peter Dalgaard             ??ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907

On Wed, 2005-08-03 at 23:24 +0200, Simone Gabbriellini
wrote:
> Dear list,
> can someone tell me why this two pieces of code give me the same  
> results?
> 
>  > for(i in 0:5){ sum[i] = i }
>  > sum
> [1] 1 2 3 4 5
> 
>  > for(i in 1:5){ sum[i] = i }
>  > sum
> [1] 1 2 3 4 5
> 
> shouldn't the first one be
> 
> 0 1 2 3 4 5
> 
> thank you,
> simone
No....the indexing of R objects is 1 based. Thus your first loop tried
to set i[0], which is a non-existent entry.
> i <- 0:5
> i
[1] 0 1 2 3 4 5
> i[0]
numeric(0)
> i[1]
[1] 0

HTH,

Marc Schwartz

Simone Gabbriellini wrote:

 > it was simple, but you know, it's always simple when you've done
it :)

Surely this homage to experience deserves nomination for the fortunes 
package.

Jim