Thanks a lot, Pratap!
Dimitri
On Mon, Feb 4, 2013 at 9:43 AM, nalluri pratap <pratap_s...@yahoo.co.in>wrote:
> Just modified your code a bit, hope this helps:
>
> a=expand.grid(1:2,1:2)
> b=expand.grid(1:2,1:2,1:2)
> c=expand.grid(1:2,1:2,1:2,1:2)
> l.long<-list(a,b,c)
> mygrid<-do.call(expand.grid,lapply(l.long,function(x) 1:nrow(x)))
> out<-vector("list",nrow(mygrid))
> for(gridrow in 1:nrow(mygrid))
> {
> sum_rows=0
> for (i in seq_along(mygrid))
> {
> myrow<-mygrid[gridrow,i]
> sum_rows=sum_rows+sum(l.long[[i]][myrow,])
> }
> out[[gridrow]]=sum_rows
> }
>
> Pratap
>
> --- On *Sun, 3/2/13, Dimitri Liakhovitski <dimitri.liakhovit...@gmail.com>
> * wrote:
>
>
> From: Dimitri Liakhovitski <dimitri.liakhovit...@gmail.com>
> Subject: [R] Looping through rows of all elements of a list that has
> variable length
> To: "r-help" <r-help@r-project.org>
> Date: Sunday, 3 February, 2013, 11:03 PM
>
> Dear R-ers,
> I have a list of data frames such that the length of the list is unknown in
> advance (it could be 1 or 2 or more). Each element of the list contains a
> data frame.
> I need to loop through all rows of the list element 1 AND (if applicable)
> of the list element 2 etc. and do something at each iteration.
> I am trying to figure out how to write a code that is generic, i.e., loops
> through the rows of all elements of my lists even if the total number of
> the list elments is unknown in advance.
> Below is an example.
>
> a=expand.grid(1:2,1:2)
> b=expand.grid(1:2,1:2,1:2)
> #################################################
> # My list that can have 1 element, e.g.:
> l.short<-vector("list",1)
> l.short[[1]]<-a
> # I need to loop through rows of l.short[[1]] and do somethinig (it's
> unimportant what exactly) with them, e.g.:
> out<-vector("list",nrow(l.short[[1]]))
> for(i in 1:nrow(l.short[[1]])){ # i<-1
> out[[i]]<-sum(l.short[[1]][i,])
> }
> (out)
>
> #################################################
> # Or my list could have >1 elements, e.g., 2 like below (or 3 or more).
> # The total length of my list varies.
>
> l.long<-list(a,b)
> # I need to loop through rows of l.long[[1]] AND of l.long[[2]]
> simultaneously
> # and do something with both, - see example below.
> # Below, I am doing it "manually" by using expand.grid to create all
> combinations of rows of 2 elements of 'l.long':
> mygrid<-expand.grid(1:nrow(l.long[[1]]),1:nrow(l.long[[2]]))
> out<-vector("list",nrow(mygrid))
> for(gridrow in 1:nrow(mygrid)){ # gridrow<-1
> row.a<-mygrid[gridrow,1]
> row.b<-mygrid[gridrow,2]
> out[[gridrow]]<-sum(l.long[[1]][row.a,])+sum(l.long[[2]][row.b,])
> }
> Thank you very much for any suggestions!
> --
> Dimitri Liakhovitski
> gfk.com <http://marketfusionanalytics.com/>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org<http://in.mc1909.mail.yahoo.com/mc/compose?to=R-help@r-project.org>mailing
> list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
>
--
Dimitri Liakhovitski
gfk.com <http://marketfusionanalytics.com/>
[[alternative HTML version deleted]]
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