Is there ever a case that X[,names(X)[4]] would give a different result than X[,4]? Or is this just a case of the "the longest distance between any 2 points is a shortcut"?
Well I guess if X has non-unique names then you might see a difference, but having a data frame with non-unique names and using the longer version above is more likely to be asking for trouble than doing anything useful. On Fri, Oct 4, 2013 at 10:15 AM, John Kane <[email protected]> wrote: > X[,names(X)[4]] works fine for me. I had never thought of doing this. > Neat idea. > > John Kane > Kingston ON Canada > > > > -----Original Message----- > > From: [email protected] > > Sent: Fri, 4 Oct 2013 12:06:50 -0400 > > To: [email protected] > > Subject: [R] quote a column of a dataframe by its name > > > > Dear All, > > > > I have a question, suppose X is a dataframe, with column names as > > "x1", "x2", "x3", ..... And I would like to use the i-th column by > > X[,'xi']. > > But it seems the single quote and double quote are different. > > So if I run X[, names(X)[i]], it has some error. > > Please use the below example code > > > > X = matrix(rnorm(50),ncol = 5) > > X = data.frame(X) > > names(X)=c("x1","x2","x3","x4","x5") > > > > #pick the 4-th column > > X[,'x4'] #working > > X[,names(X)[4]] # not working , so how to modify this line? > > > > names(X)[4] # returns "x4" > > sQuote(names(X)[4]) # returns "'x4'" > > > > > > Best, > > > > ______________________________________________ > > [email protected] 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. > > ____________________________________________________________ > FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on > your desktop! > > ______________________________________________ > [email protected] 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. > -- Gregory (Greg) L. Snow Ph.D. [email protected] [[alternative HTML version deleted]] ______________________________________________ [email protected] 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.
