Re: [Rd] non user-friendly error for chol2inv functions

From: Martin Maechler <maechler_at_stat.math.ethz.ch>
Date: Fri, 29 Aug 2008 15:00:01 +0200

>>>>> "cd" == christophe dutang <dutangc_at_gmail.com> >>>>> on Fri, 29 Aug 2008 14:28:42 +0200 writes:

    cd> Yes, I do not cast the first argument as a matrix with as.matrix function.     cd> Maybe we could detail the error message if the first argument is a numeric?

    cd> error(_("'a' is a numeric and must be coerced to a numeric matrix"));

Merci, Christophe. Yes, we *could* do that. Alternatively, I think I will just make it work in that case, since I see that

      qr(), chol(), svd(), solve() all treat a numeric (of length 1) as a 1 x 1 matrix automatically.

    cd> Thanks for your answer
De rien!

Martin

    cd> 2008/8/29 Martin Maechler <maechler_at_stat.math.ethz.ch>

>> >>>>> "cd" == christophe dutang <dutangc@gmail.com>
>> >>>>> on Fri, 29 Aug 2008 12:44:18 +0200 writes:
>>
    cd> Hi,
    cd> In function chol2inv with the option LINPACK set to false (default),
>> it

    cd> raises an error when the matrix is 1x1 matrix (i.e. just a real)
>> saying
>>

    cd> 'a' must be a numeric matrix
>>
>> It is very helpful, but you have to read and understand it.
>> I'm pretty sure you did not provide a 1 x 1 matrix.
>>
>> Here's an example showing how things works :
>>
>> > m <- matrix(4,1,1)
>> > cm <- chol(m)
>> > cm
>> [,1]
>> [1,] 2
>> > chol2inv(cm)
>> [,1]
>> [1,] 0.25
>> >
>>
>> Martin Maechler, ETH Zurich
>>
>>
    cd> This error is raised by the underlying C function (modLa_chol2inv in     cd> function Lapack.c). Everything is normal, but I wonder if we could
>> have

    cd> another behavior when we pass a 1x1 matrix. I spent time this
>> morning

    cd> finding where was the error, and it was this "problem".
>>

    cd> Thanks in advance
>>

    cd> Christophe
>>

    cd> [[alternative HTML version deleted]]
>>

    cd> ______________________________________________
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>>

    cd> [[alternative HTML version deleted]]

    cd> ______________________________________________
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