cond(zeros(4))

[John W. Eaton]

On 29-Jun-1999, address@hidden <address@hidden> wrote:

| I type in
| 
| cond(zeros(4))
| 
| and get NaN.  I know this is the IEEE analogue of the strict 
| mathematical definition, but since I'm using this quantity to 
| test how close a matrix is to singular, it would have been nicer 
| to get Inf.

OK, I've fixed this in my sources using the following logic:

    if (any (any (isinf (a) | isnan (a))))
      error ("cond: argument must not contain Inf or NaN values");
    else
      sigma = svd (a);
      sigma_1 = sigma(1);
      sigma_n = sigma(length (sigma));
      if (sigma_1 == 0 || sigma_n == 0)
        retval = Inf;
      else
        retval = sigma_1 / sigma_n;
      endif
    endif

Does anyone see a problem with that?

BTW, please report bugs to the bug-octave mailing list.

Thanks,

jwe



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