Hello,
You can split the filenames vector according to a pattern,
filenames <- c("a1.csv", "a2.csv", "b1.csv", "b2.csv", "c1.csv", "c2.csv")
fnpattern <- gsub("[[:digit:]]", "", filenames)
df.groups <- split(filenames, fnpattern)
and then use this list to process each of the groups of data.frames in
'alldata', possibly using lapply.
Hpe this helps,
Rui Barradas
BustedAvi wrote
>
> Hi all,
>
> I'm just a beginner with R but I have not been able to search for any
> relevant answer to my problem. I apologize if it has in fact been asked
> before.
>
> Recently I've realized that I need to combine hundreds of pairs of data
> frames. The filenames of the frames I need to combine have unique
> strings.
> This is my best guess as to the approach to take:
>
> filenames<-list.files()
>
> filenames
> [1] "a1.csv" "a2.csv" "b1.csv" "b2.csv" "c1.csv" "c2.csv"
>
> alldata<-lapply(filenames, read.csv, header=TRUE)
>
> names(alldata)<-filenames
> summary(alldata)
> Length Class Mode
> a1.csv 27 data.frame list
> a2.csv 27 data.frame list
> b1.csv 27 data.frame list
> b2.csv 27 data.frame list
> c1.csv 27 data.frame list
> c2.csv 27 data.frame list
>
> My next step would be to cbind files that share a common string at the
> beginning, such as:
> cbind(alldata[[1]],alldata[[2]])
> cbind(alldata[[3]],alldata[[4]])
> cbind(alldata[[5]],alldata[[6]])
> ...
>
> but file list is hundreds of files long (but is sorted alphanumerically
> such as in this example - not sure if this is relevant). If I had to
> guess, I'd do something like this:
>
> which(names(alldata)==...), to identify which elements to combine based on
> unique filename
>
> OR
> x<-seq(1,length(alldata), 2)
> y=x+1
> z<-cbind(x,y)
> z
> x y
> [1,] 1 2
> [2,] 3 4
> [3,] 5 6
>
> to use the frame created in z to combine based on rows,
>
> then use a looped cbind function (or *apply function with nested cbind
> function?) using the previously returned indexes to create my new combined
> data frames, including a step to write the frames to a new unique filename
> (not sure how to do that step in this context). These last steps I've
> tried a lot of code but nothing worth mentioning as it has all failed
> miserably.
>
> I appreciate the help,
>
> M
>
> [[alternative HTML version deleted]]
>
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>
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