[R] local and global variables

[Duncan Murdoch]

On 20/04/2010 4:27 AM, n.vialma at libero.it wrote:
> Hi all,
> I have a question about global and local variables.First of all, a variable 
> defined in a for loop is it a local or global variable??
>   

R doesn't create a local scope for "for" loops.  So it will have the 
same scope as other variables created in the same scope.
> Second, I'm trying to build a loop in the following way:
> I have these 3 data frames
> bilanci_2005<-bilanci1[ANNO==2005,]
> bilanci_2006<-bilanci1[ANNO==2006,]
> bilanci_2007 <--bilanci1[ANNO==2007,]
>
> LOOP:
> v=list(2005,2006,2007)      
>   

I would recommend using c(2005,2006, 2007) rather than list(), but I 
don't think that has much effect.
> for (a in v){
> anno1=a
> anno2=a+1
> for (i in 1:length(bilanci_a)) {
>   

Using the name of one variable as part of another name won't cause it to 
be magically expanded.  You should have set things up differently from 
the beginning:

bilanci_subsets <- list("2005" = bilanci1[ANNO==2005,],
                                 "2006" = bilanci1[ANNO==2006,],
                                 "2007" = bilanci1[ANNO==2007,] )

Then you can use

for (i in names(bilanci_subsets)) {
  .... bilanci_subsets[[i]] ....

Duncan Murdoch
> assign(paste(""bilanci",anno1,anno2,sep=""), rbind(paste("bilanci",anno1,anno2,
> sep=""),
>                           bilanci_anno2[bilanci_anno2$CFISCALE==bilanci_anno1
> [i,]$CFISCALE,],
>                           "bilanci_anno1[i,])
> }
> }
>  what I'm trying to do is for example to give the contents of   a (so the 
> values which are in the list named v) to the bilanci variable. In Stata this 
> means using a particular kind of  "".
> How can I do this in R?
>
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