On 25.05.2012 16:42, Ken wrote:
Matthew Ouellette<mouellette89<at> gmail.com> writes: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]]) ...
I think the actual question is how to cbind() all data.frames. The answer for that is:
result <- do.call(cbind, alldata) Best, Uwe Ligges
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]]Hi Matthew, You could try using substr() if the cbind is based on a common string in the file name just makes sure that the strings in filenames is in the same order as the files are in list.files: a1<- data.frame("col1" = seq(1,10, 1)) a2<- data.frame("col2" = seq(11,20, 1)) b1<- data.frame("col3" = seq(21,30, 1)) b2<- data.frame("col4" = seq(31,40, 1)) filenames<- c("a1", "a2", "b1", "b2") list.files<- list(a1, a2, b1, b2) first.letter<- substr(filenames, 1,1) unique.first.letter<- unique(first.letter) l.files<- list() for(i in 1:length(unique.first.letter)){ l.files[[i]] = as.data.frame(list.files[first.letter == unique.first.letter[i]]) } HTH, Ken ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.
______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.
