[Rd] qr.qy and qr.qty give an error message when y is integer and LAPACK=TRUE

Martin Maechler maechler at stat.math.ethz.ch
Mon Dec 3 16:17:35 CET 2012

>>>>> Berend Hasselman <bhh at xs4all.nl>
>>>>>     on Mon, 3 Dec 2012 15:25:21 +0100 writes:

    > With this example

    > set.seed(123) A <- matrix(runif(40), nrow = 8) y <-
    > 1:nrow(A)

    > A.laqr <- qr(A, LAPACK=TRUE)

    > both qr.qy(A.laqr,y) and qr.qty(A.laqr,y) give the
    > respective error messages

    > Error in qr.qy(A.laqr, y) : 'b' must be a numeric matrix
    > Error in qr.qty(A.laqr, y) : 'b' must be a numeric matrix

    > However when Lapack is not used as in

    > A.liqr <- qr(A, LAPACK=FALSE)

    > qr.qy(A.liqr,y) and qr.qty(A.liqr,y) don't issue error
    > messages.

You are right... if you look at R 2.15.2 (or even it's patched

    > Looking at the source of qr.qy and qr.qty in
    > https://svn.r-project.org/R/trunk/src/library/base/R/qr.R

Hmm, no: If  you really looked at that code (during the last several weeks),
you would have noted that the code has *changed* from what you
give below...

and the current R development version uses  
.Internal(.) instead of .Call()  and the C code behind the
.Internal() nicely deals with integer 'y' as well.

In short, this is already fixed in R, since ~ September,
but it won't probably be fixed in "R 2.15.2 patched" ...

Thank you for the report, anyway!

    > I see that in the case of Lapack the storage.mode of y is
    > not set to "double" (in contrast to when Linpack QR has
    > been used).

    > I assume that the error issued when LAPACK=TRUE is not
    > intended.

    > Berend

    > Suggested code change in qr.qy Replace

    >     if(!is.null(a) && is.logical(a) && a)
    > return(.Call("qr_qy_real", qr, as.matrix(y), 0, PACKAGE =
    > "base"))

    > with

    >     if(!is.null(a) && is.logical(a) && a) {
    > storage.mode(y) <- "double" return(.Call("qr_qy_real", qr,
    > as.matrix(y), 0, PACKAGE = "base")) }

    > and a similar change in qr.qty
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