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sprand/sprandn fourth parameter implementation


From: Eduardo
Subject: sprand/sprandn fourth parameter implementation
Date: Tue, 4 Mar 2014 16:04:08 +0100

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)

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