Michela Leonardi wrote:
Dear R-Help Members, I am trying to read and analyse a set of 100 csv files. I need work only on some columns in each of those, so I decided to use a for loop, isolate the column in each file to work on, but then an error mesage appear: "undefined columns selected" Here is my code: setwd("F:/Data/") a<-list.files() for (x in a) { u<-read.csv(x, header=T, sep=",", check.names=FALSE) #it give me the same problem using read.table h<-u[,2] } Error in `[.data.frame`(u, , 2) : undefined columns selected It does not give me any problem selecting ane entire row (e.g. u[2,]) or a single value (e.g. [5,2]) If I try to select a column after the for loop I does not show any problem, e.g.: a<-list.files() for (x in a) { u<-read.csv(x, header=T, sep=",", check.names=FALSE) } h<-u[,2] I would appreciate any suggestion or pointer to solve the problem or to do the same thing in a different way. Thanks for your consideration
Michela, What are your loops supposed to accomplish? They just give you the last file in 'a'. When you get the error, that indicates that at least one of your files has only one column. You don't get the error when you take h<-u[,2] out of the loop because the last file in 'a' does happen to have 2 or more columns. You need to rethink the loop with regard to what you will do with 'h'. And you need to check what's in those files. -Peter Ehlers
-- Michela Leonardi ______________________________________________ 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.