Sort across multiple csv
On May 18, 2012, at 12:56 PM, Matthew Ouellette wrote:
Dear R help list, I am very new to R and I apologize in advance if this has been answered before. I have done my best to google/R search what I need but no luck. Here is what I am attempting: I have hundreds of .csv files that I need to sort based on a single column of alphanumeric data. All of the files contain matrices that have identical dimensions and headers, however the data table doesn't begin until the 74th line in each file. Doing some searching, I have been able to create an object with elements consisting of each file in the folder containing the targets (please note this is my working directory): filenames<-list.files() alldata<-lapply(filenames, read.csv, skip=73, header=TRUE) At this point I believe I have created an object with N elements (where N=# files in the wd), each containing the matrix I am attempting to sort. I am completely lost as to how I can sort each matrix
You should learn to use precise terminology to refer to R objects. You have a list of dataframes (not matrices) You can loop over then and return a list of transformed (.e.g. sorted) dataframes: alldata <- lapply (alldata, function(x) x[order(x[["Name"]], ] )
based on a single column (say, "Name") and then either overwrite
The above code would overwrite.
the source files or write to a new directory all of the sorted data.
If you didn't want it overwritten then assign it to a different name.
I half wonder if I should be creating individual objects for each file that I read in, but I haven't been able to figure this out either.
Much better to stick with lists.
Please note that I am trying to sort these files individually - would a loop be more efficient?
`lapply` is really a loop.
I appreciate the help, BustedAvi [[alternative HTML version deleted]]
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