But one could argue that <= could also mean assignment (although as a mathematician I'd go with implies or perhaps 'is implied by') and wouldn't have the problem highlighted below. Similarly one could use the Pascal := for assignment. So although the idea of having two different operators for 'is equal to' and 'make equal to' makes sense what we have today isn't neccesarily right - we got rid of '_' as assignment for example.
-------------------------- David Jessop Global Head of Quantitative Research UBS Investment Research +44 20 7567 9882 ----- Original Message ----- From: r-help-boun...@r-project.org <r-help-boun...@r-project.org> To: Horace Tso <horace....@pgn.com> Cc: r-help <r-help@r-project.org> Sent: Fri Jun 18 23:26:23 2010 Subject: Re: [R] questions on some operators in R On Fri, Jun 18, 2010 at 2:15 PM, Horace Tso <horace....@pgn.com> wrote: > Li li, > > I know many S-language old timers would tell you to use <- over = for > assignment. Speaking from my own painful experience of debugging S/R codes, I > much much much prefer '='. In fact, I'd like to see the R language get ride > of '<-' as the assignment operator. > > Here is why. > >> x = -5:10 >> x > [1] -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 > > Now I want to find elements of x which are smaller than negative 2, or -2. So > naturally I'd do, > >> which(x<-2) > Error in which(x <- 2) : argument to 'which' is not logical > > Oops, what happened? If you look up help pages for 'which', you'd find no > clue. > > What occurred in the parenthesis is that you've overidden your vector x with > a single value of 2, thanks to the assignment operator '<-'. > > This' a big problem not just because you might end up spending hours finding > out what's wrong with such innocent expression. The worst part is, you'd have > lost your vector x forever. Just image if x is 1200 by 1200 matrix. > I prefer <- because it makes more sense. It evokes the idea of assignment, which is what it is, whereas = reminds one of equality which is wrong since its not equality but assignment. Its also consistent with <<- whereas it seems highly inconsistent to use = and <<- . Its also less ambiguous when not used on the left hand side of a statement. ______________________________________________ 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.
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______________________________________________ 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.
