[R-sig-Geo] loop- changing varible names

[Roger Bivand]

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Comment inline below:


On Wed, 22 Aug 2012, K Jjw wrote:

> Hi ? I am trying to loop over some data while changing the variable 
> names. ? My code right now looks like ? 
> months<-c(5,4,8,1,9,7,6,2,12,11,10,3) 
> mnth_nme<-c("jan","feb","mar","apr","may","jun","jul","aug","sep","oct","nov","dec") 
> a<-1 ? for (i in months) { ? had_1990<-raster(prec,months) ? 
> had_2040<-raster(tot_40,months) ? had_2090<-raster(tot_90,months) ? #all 
> the?month data ? 
> paste(mnth_nme[a],"_ppt",sep="")<-stack(had_1990,had_2040,had_2090)### 
> this? is where it breaks down. ? a<-a+1 ? } ? Basically I want to end up 
> with each month's data stacked and called jan_ppt, feb_ppt.... ? I tried 
> to google the solution and people seem to suggest lists but when I tried 
> to make a list I got another error and I am not sure what I am doing 
> wrong ?> months<-c(5,4,8,1,9,7,6,2,12,11,10,3) > 
> mnth_nme<-c("jan","feb","mar","apr","may","jun","jul","aug","sep","oct","nov","dec") 
> > a<-1 > mnth <- list() > for(i in mnth_nme) + { + 
> mnth[[paste(mnth_nme[a]"_ppt",sep="")]] Error: unexpected string 
> constant in: "{ mnth[[paste(mnth_nme[a]"_ppt"" ?

Your HTML-mail is not easy to read, and HTML misformatting may lead to 
confusion. You should read error messages carefully:

Error: unexpected string constant in: "{ mnth[[paste(mnth_nme[a]"_ppt""

seems clear enough, as you (probably) omitted a comma in the paste() call. 
When putting things in loops, do simplify and echo to console:

comp_nm <- paste(mnth_nme[a], "ppt", sep="_")
cat(comp_nm, "\n")
mnth[[comp_nm]] <- ...

to see what is going on, removing the in-loop console output when you know 
it works. Arguably the _ppt in the variable name is redundant anyway, 
isn't it?

Roger

> Any explanation would be very helpful. Thanks
> ?
> KJ
> 	[[alternative HTML version deleted]]
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no