[R] Assignment to variables fails to loop

[jim holtman]

Look at what

paste("Fekete_",index$year, index$month, sep='')

is creating in the 'assign'; it is a character vector that have the
same value each time through the loop.  What you may want to do is
something like this:

index <- expand.grid(year = sprintf("%04d", seq(1986, 1995)), month =
sprintf("%02d", 1:12))


# Assign file names to individual objects with variable name components

for (i in seq(nrow(index))) {
         assign(paste("Fekete_",index$year[i], index$month[i], sep=''),
            read.table(file=paste("C:\\Documents and
Settings\\Data\\comp_runoff_hd_", index$year[i],
                index$month[i], sep=""), header=FALSE, sep=" "))


         update <- substr(i,35,55) # substring - 2nd argument is
character at which extraction is to begin, 3rd argument is where
extraction ends.
         print(c("LOADED FILE:",update), quote=FALSE)
         }

On Fri, Mar 27, 2009 at 2:11 PM, Steve Murray <smurray444 at hotmail.com> wrote:
>
> Dear all,
>
> I think I'm nearly there in writing R code which will read in files with two variable parts to the file name and then assigning these file names to objects, which also have two variable parts. I have got the code running without encountering errors, however, I receive 50+ of the same warnings:
>
> 1: In assign(paste("Fekete_", index$year, index$month, sep = ""),  ... :
>  only the first element is used as variable name
>
> And it's true, when I do ls() only Fekete198601 has been assigned. I've attempted to rectify this, but have only come up against further errors.
>
> The code as it stands, is as follows:
>
>
> # READ IN FILES FROM DISK
>
> # File names have two variable parts: creating a 'file index' is a two-step process
>
> index <- expand.grid(year = sprintf("%04d", seq(1986, 1995)), month = sprintf("%02d", 1:12))
> filelist <- paste("C:\\Documents and Settings\\Data\\comp_runoff_hd_", paste(index$year, index$month, sep=''), '.asc', sep='')
>
> filelist
>
>
> # Assign file names to individual objects with variable name components
>
> for (i in filelist) {
>          assign(paste("Fekete_",index$year, index$month, sep=''),read.table(file=i, header=FALSE, sep=" "))
>
>
>          update <- substr(i,35,55) # substring - 2nd argument is character at which extraction is to begin, 3rd argument is where extraction ends.
>          print(c("LOADED FILE:",update), quote=FALSE)
>          }
>
>
>> ls()
> [1] "Fekete_198601" "filelist"      "i"             "index"
> [5] "update"
>
>
> Why is it that only Fekete_198601 has had data assigned to it (there should be 120 such objects in total) and how do I go about solving this?
>
>
> Many thanks again for any help offered,
>
>
> Steve
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?