Eduard, are we discussing the same thing again :)? Wasn't this somehow your question as well.. the discrepancy between:
dt[, a] and dt[, "a", with=FALSE]. There should be a drop=TRUE/FALSE option (as in the case of data.frame) that should be used when you use `with=FALSE`. Until then, the default option seems to be drop=FALSE, which results in a data.table. Alexandre, as of now, it could be done as Eduard points out. Arun On Friday, May 17, 2013 at 4:59 PM, Eduard Antonyan wrote: > 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] > (mailto:[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] > > (mailto:[email protected]) > > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > > _______________________________________________ > datatable-help mailing list > [email protected] > (mailto:[email protected]) > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > >
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