R help - Feb 2010 - replace a for loop

Hi everybody!

I'm still quite new in R and I don't really understand this whole 
"vectorization" thing.
For now, I use a for loop (and it works fine), but I think it would be 
useful to replace it.

I want to export the result of a test statistic, which is stored as a 
list, into a csv file. I therefore have to export each element of the 
list separately.
Here is the code:
----
str(test)
List of 3
  $ output : num [1:15, 1:6] 1 2 3 4 5 6 7 8 9 10 ...
   ..- attr(*, "dimnames")=List of 2
   .. ..$ : NULL
   .. ..$ : chr [1:6] "con.num" "psihat" "p.value"
"p.crit" ...
  $ con    : num [1:6, 1:15] 1 -1 0 0 0 0 1 0 -1 0 ...
  $ num.sig: int 0

for (i in 1:3){
  write.csv(test[[i]], file="filename.csv", append=T, quote=F,
row.names=T)
}
----

As I said, I don't completely understand, but I think one of these 
"apply" function might do what I need.

Thanks in advance
Ivan

On Wed, Feb 10, 2010 at 9:50 AM, Ivan Calandra
<ivan.calandra at uni-hamburg.de> wrote:
> I'm still quite new in R and I don't really understand this whole
> "vectorization" thing.
>
See [1] for an article on vectorisation and loops in R.
Liviu

[1] http://www.r-project.org/doc/Rnews/Rnews_2008-1.pdf

After reading the R news, I've tried this code and it works:
 > rapply(list(names(test),test), write.csv, file="filename.csv", 
append=T, row.names=F)

However, the output is structured like this:
names(test)[[1]]
names(test)[[2]]
etc...
test[[1]]
test[[2]]
etc...

I would like to alternate names(test) and test in the output. The 
desired output would be structured like this:
names(test)[[1]]
test[[1]]
names(test)[[2]]
test[[2]]
etc...

Can someone guide me for that step? Better solutions for the whole thing 
are of course welcomed!

Thanks a lot
Ivan

Le 2/10/2010 10:50, Ivan Calandra a ?crit :
> Hi everybody!
>
> I'm still quite new in R and I don't really understand this whole 
> "vectorization" thing.
> For now, I use a for loop (and it works fine), but I think it would be 
> useful to replace it.
>
> I want to export the result of a test statistic, which is stored as a 
> list, into a csv file. I therefore have to export each element of the 
> list separately.
> Here is the code:
> ----
> str(test)
> List of 3
>  $ output : num [1:15, 1:6] 1 2 3 4 5 6 7 8 9 10 ...
>   ..- attr(*, "dimnames")=List of 2
>   .. ..$ : NULL
>   .. ..$ : chr [1:6] "con.num" "psihat"
"p.value" "p.crit" ...
>  $ con    : num [1:6, 1:15] 1 -1 0 0 0 0 1 0 -1 0 ...
>  $ num.sig: int 0
>
> for (i in 1:3){
>  write.csv(test[[i]], file="filename.csv", append=T, quote=F, 
> row.names=T)
> }
> ----
>
> As I said, I don't completely understand, but I think one of these 
> "apply" function might do what I need.
>
> Thanks in advance
> Ivan
>
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