On 6/5/2006 5:30 AM, [EMAIL PROTECTED] wrote: >>>>>> "FrPi" == François Pinard <[EMAIL PROTECTED]> >>>>>> on Sun, 4 Jun 2006 06:27:53 +0200 (CEST) writes: > > FrPi> Hi, people. > FrPi> xy.coords() does not behave like its documentation says, when given > some > FrPi> matrices. ?xy.coords says: > > FrPi> If 'y' is 'NULL' and 'x' is a [...] formula [...] list [...] > FrPi> time series [...] matrix with two columns [...] > > FrPi> In any other case, the 'x' argument is coerced to a vector and > FrPi> returned as *y* component [...] > > FrPi> Now, consider this short transcript: > > FrPi> > ======================================================================> > >> as.vector(rbind(1, 2, 3)) > FrPi> [1] 1 2 3 > >> as.vector(cbind(1, 2, 3)) > FrPi> [1] 1 2 3 > >> xy.coords(rbind(1, 2, 3)) > FrPi> $x > FrPi> [1] 1 2 3 > > FrPi> $y > FrPi> [1] 1 2 3 > > FrPi> $xlab > FrPi> [1] "Index" > > FrPi> $ylab > FrPi> NULL > > >> xy.coords(cbind(1, 2, 3)) > FrPi> $x > FrPi> [1] 1 > > FrPi> $y > FrPi> [1] 2 > > FrPi> $xlab > FrPi> [1] "[,1]" > > FrPi> $ylab > FrPi> [1] "[,2]" > > FrPi> > ======================================================================< > > FrPi> A 3 x 1 matrix and a 1 x 3 matrix both fall in the "In > FrPi> any other case" category, but it seems that only the 3 x 1 > FrPi> is really "coerced to a vector". > > yes. So you are right: There's a bug > > FrPi> The R code for xy.coord() suggests that the documentation should > read > FrPi> "matrix with at least two columns" instead of "matrix with two > columns". > > FrPi> As a user, I was really expecting the coercion to a > FrPi> vector to happen. What triggered me into exploring > FrPi> this problem is the fact that plot() showed a single > FrPi> point where I was expecting many. If you decide that > FrPi> the code is right and the documentation is wrong, then > FrPi> I would suggest that the code be a bit more friendly, > FrPi> by at least issuing some warning if more than two > FrPi> columns are given to a matrix. > > I agree. > > I'm not sure what the change should be -- and am asking for useR > feedback here : > > 1) give an error in the case of a matrix (or data.frame) with '> 2' columns > 2) give a warning, and use the first 2 columns -- as it happens now > 3) silently coerce to vector -- as the current documentation claims. > > The most clean would be "1)", but given back compatibility, etc, > my tendency would go into the direction of "2)".
I think the current behaviour is reasonable, and shouldn't lead to warnings when executed. If you meant a warning in the man page, that would be fine. I'm not so sure about some undocumented behaviour for formulas: x <- 1:10 y <- 11:20 z <- 21:30 xy.coords(y ~ x+z) will set the x column to the sum of x+z. That's not the usual way formulas are handled. I'd be happier with picking out one column, or generating an error, instead. I think the error message might have been the intention, because there's a test if (inherits(x, "formula") && length(x) == 3) but length(y ~ x+z) is 3. I think the test should be if (inherits(x, "formula") && length(x) == 3 && length(x[[2]]) == 1 && length(x[[3]]) == 1) Duncan Murdoch > > > FrPi> Another problem in the same area: the documentation lies about how > the > FrPi> function acts when given a data.frame. From the code, a data.frame > is > FrPi> processed as if it was a matrix. From the documentation, while the > FrPi> data.frame is not mentioned explicitely, it is implied in the > paragraph > FrPi> explaining how a list is processed (because a data.frame is a list). > FrPi> Some reconciliation is needed here as well. > > Yes; in this case, I propose to just amend the documentation > explainining that data.frames are treated "as matrices". > > Thanks a lot, Francois, for your careful reading and > careful report! > [ Though I do slightly mind the word "lies" since > I do value the 9th commandment.. > Not telling the truth *accidentally* is not "lying" ] > > Martin Maechler, ETH Zurich > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
