Ricardo added a bug report here on this topic: https://r-forge.r-project.org/tracker/index.php?func=detail&aid=5008&group_id=240&atid=975 But I don't think having duplicate names is an easy-to-implement concept. For ex:
dt <- data.table(x=1:3, x=4:6, y=c(1,1,2)) dt[, print(.SD), by=y] x 1: 1 2: 2 x 1: 3 .SD loses the second "x". Also, some other questions become difficult to handle. Ex: dt <- data.table(x=c(1,1,2,2), y=c(1,2,3,4), x=c(2,2,1,1)) dt[, list(x=x/x[1], y=y), by=x] Which "x" should be choose for which operation? Arun On Friday, November 1, 2013 at 10:59 PM, Eduard Antonyan wrote: > Having duplicate names is allowed and not that unusual in data.table > framework, so there is no need to signal anything here. > > A different question is whether there should be a warning here: > > dt = data.table(a = 1, a = 2) > dt[, a] > > and I think that'd be a pretty good FR to have. > > > On Fri, Nov 1, 2013 at 4:49 PM, Alexandre Sieira <[email protected] > (mailto:[email protected])> wrote: > > I found this behavior during a debugging session: > > > > > d = data.table(a=1, b=2, c=3) > > > setnames(d, "a", "b") > > > d > > b b c > > 1: 1 2 3 > > > > Shouldn’t setnames() check if the new column names already exist before > > renaming, and signal an error or at least a warning if they do? > > -- > > 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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