Be careful with the idiom x[, -which(columnIsBad)] If no columns are bad this leads to x[, -integer(0)] which is a data.rame with no columns, exactly the opposite of what you want. x[, !columnIsBad] doesn't have that problem. However, if you can't tell if a column is bad or not (i.e., columnIsBad contains an NA) you will have to process columnIsBad to turn that NA into a definite TRUE or FALSE.
Finally, add the drop=FALSE argument to [] in case the result would be a one-column data.frame to prevent it from being converted to the column itself. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf Of jim holtman > Sent: Thursday, October 13, 2011 6:24 AM > To: Samir Benzerfa > Cc: r-help@r-project.org > Subject: Re: [R] delete columns which partially match expression > > try this: > > > x <- read.table(textConnection("A B C D > > E > + 12 33 Error1 71 Error2 > + 12 33 Error1 71 Error2 > + 12 33 Error1 71 Error2 > + 12 33 Error1 71 Error2 > + 12 33 Error1 71 Error2") > + , as.is = TRUE > + , header = TRUE > + ) > > closeAllConnections() > > colMatch <- which(apply(x, 2, function(a) any(grepl("Error", a)))) > > colMatch > C E > 3 5 > > # delete columns > > x[, -colMatch] > A B D > 1 12 33 71 > 2 12 33 71 > 3 12 33 71 > 4 12 33 71 > 5 12 33 71 > > > > > On Thu, Oct 13, 2011 at 9:10 AM, Samir Benzerfa <benze...@gmx.ch> wrote: > > Hello everyone, > > > > > > > > I'd like to search for certain "expressions" (characters) in my data.frame > > and delete the containing columns. > > > > > > > > So, for example in the below table, I'd like to delete all columns which > > contain the expression "Error". That is, R should delete column C and E from > > my data. Any ideas? > > > > > > > > A B C D E > > > > 12 33 Error1 71 Error2 > > > > > > > > Cheers, S.B. > > > > > > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. > > > > > > -- > Jim Holtman > Data Munger Guru > > What is the problem that you are trying to solve? > > ______________________________________________ > 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.
