[Numpy-discussion] matrix norm

Jason Grout jason-sage at creativetrax.com
Mon Oct 22 15:04:44 EDT 2012

On 10/22/12 10:44 AM, Jason Grout wrote:
> I'm curious why scipy/numpy defaults to calculating the Frobenius norm
> for matrices [1], when Matlab, Octave, and Mathematica all default to
> calculating the induced 2-norm [2].  Is it solely because the Frobenius
> norm is easier to calculate, or is there some other good mathematical
> reason for doing things differently?

I think we've established that the other software mentioned does indeed 
use the spectral norm by default.  I'm still curious: what was the 
reason for breaking with the norm (pun intended :)?  Any chance that in 
a (probably far distant) future release, the norm default could be 
changed to conform with matlab/octave/mathematica's view of the world? 
It's not a huge deal to me now that I know to watch out for it, but it 
did just bite me and a student a few times.



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