Use dt[[colname]], but this seems like a bug to me - I would've thought that dt[, a] and dt[, "a", with = F] should return the exact same thing.
On Fri, May 17, 2013 at 9:42 AM, Alexandre Sieira < [email protected]> wrote: > Sorry if this is a basic question. > > > I'm using R 3.0.0 and data.table 1.8.8. The documentation for 'j' states > that "A single column or single expression returns that type, usually a > vector." > > > I am able to obtain this behavior if I know the column name in advance: > > > > dt = data.table(a=c(1, 2, 3), b=c(4, 5, 6)) > > > dt > > a b > > 1: 1 4 > > 2: 2 5 > > 3: 3 6 > > > str(dt[,a]) > > num [1:3] 1 2 3 > > > However, if I don't, no such luck: > > > colname="a" > > str(dt[,colname,with=F]) > Classes ‘data.table’ and 'data.frame': 3 obs. of 1 variable: > $ a: num 1 2 3 > - attr(*, ".internal.selfref")=<externalptr> > > If there a way to extract an entire column as a vector if I have the > column name as a character scalar? > > Thank you! > > -- > Alexandre Sieira > CISA, CISSP, ISO 27001 Lead Auditor > > "The truth is rarely pure and never simple." > Oscar Wilde, The Importance of Being Earnest, 1895, Act I > > _______________________________________________ > datatable-help mailing list > [email protected] > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help >
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