On Thu, Mar 17, 2011 at 10:32 AM, Joshua Ulrich <josh.m.ulr...@gmail.com> wrote: > On Wed, Mar 16, 2011 at 6:58 PM, jctoll <jct...@gmail.com> wrote: >> Hi, >> >> I'm struggling to figure out the way to change the name of a column >> from within a loop. The problem is I can't refer to the object by its >> actual variable name, since that will change each time through the >> loop. My xts object is A. >> >>> head(A) >> A.Open A.High A.Low A.Close A.Volume A.Adjusted A.Adjusted.1 >> 2007-01-03 34.99 35.48 34.05 34.30 2574600 34.30 11867800000 >> 2007-01-04 34.30 34.60 33.46 34.41 2073700 34.41 11905860000 >> 2007-01-05 34.30 34.40 34.00 34.09 2676600 34.09 11795140000 >> 2007-01-08 33.98 34.08 33.68 33.97 1557200 33.97 11753620000 >> 2007-01-09 34.08 34.32 33.63 34.01 1386200 34.01 11767460000 >> 2007-01-10 34.04 34.04 33.37 33.70 2157400 33.70 11660200000 >> >> It's column names are: >>> colnames(A) >> [1] "A.Open" "A.High" "A.Low" "A.Close" >> "A.Volume" "A.Adjusted" "A.Adjusted.1" >> >> I want to change the 7th column name: >>> colnames(A)[7] >> [1] "A.Adjusted.1" >> >> I need to do that through a reference to i: >>> i >> [1] "A" >> >> This works: >>> colnames(get(i))[7] >> [1] "A.Adjusted.1" >> >> And this is what I want to change the column name to: >>> paste(i, ".MarketCap", sep = "") >> [1] "A.MarketCap" >> >> But how do I make the assignment? This clearly doesn't work: >> >>> colnames(get(i))[7] <- paste(i, ".MarketCap", sep = "") >> Error in colnames(get(i))[7] <- paste(i, ".MarketCap", sep = "") : >> could not find function "get<-" >> >> Nor does this (it creates a new object "A.Adjusted.1" with a value of >> "A.MarketCap") : >> >> assign(colnames(get(i))[7], paste(i, ".MarketCap", sep = "")) >> >> How can I change the name of that column within my big loop? Any >> ideas? Thanks! >> > I usually make a copy of the object, change it, then overwrite the original: > > tmp <- get(i) > colnames(tmp)[7] <- "foo" > assign(i,tmp) > > Hope that helps. > >> Best regards, >> > Joshua Ulrich | FOSS Trading: www.fosstrading.com
Thank you, that does help. It sounds like your way is similar to the way David suggested. At least now I can just resign myself to doing it that way rather than torturing my mind trying to figure out a shorter way. Thanks, James ______________________________________________ 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.