Re: sprand/sprandn fourth parameter implementation

[fgnievinski]

Eduardo wrote
> The prototype of the function: R = sprand(m,n,density,rc)
> 
> I am trying to implement that missing feature in octave, but I am really
> getting stuck here. The fourth parameter is rc:
> 1) If rc is scalar, then it is the reciprocal condition number that the
> random sparse matrix generated should approximately has.
> 
> 2) If rc is a vector of length lr, where lr <= min(m,n), then R has rc as
> its first lr singular values, all others are zero
> 
> Any one have information on how to tackle that problem?... seems not to be
> trivial. It would be something about starting from the point of a diagonal
> matrix with the single values that are specified in rc vector and then do
> random ortogonal transformations to that matrix, but changing it in a way
> that it becomes random and sparse with a concrete density.
> This is the reason I asked for looking into Matlab code in the IRC
> channel,
> I don't know if there is actually an available algorithm to do that in the
> literature.
> 
> Any information about that?
> 
> Eduardo (edu159)

Dear Eduardo, you must refrain from looking into the Matlab code, which
would be like cheating on a test -- absolutely unacceptable.

Where have you searched so far?  Any of books.google.com or
scholar.google.com or wikipedia.org?

-F.



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