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From Al Chou <>
Subject Re: [math] Matrix subMatrix and mean methods
Date Sun, 03 Oct 2004 19:05:20 GMT
--- Kim van der Linde <> wrote:
> Phil Steitz wrote:
> > I agree here as well. Do you see use cases where you will want to start 
> > with a double[][] array, perform matrix operations on it (say some 
> > decomposition) and then run stats on the resulting matrix? Will it be 
> > too onerous to make copies of the double[][] at each stage?  If so, we 
> > need to think about access to the double[][].
> I think keeping getData() will do the job. I generally do not like to 
> store the result of a calculation in the original matrix, it always 
> confuses me. If the content is of a different type, the name should be 
> different.
> >> Is there the intention to add an EigenvalueDecomposition class to the 
> >> package? In that case, which algorithm is targeted to be used? Jacobi?
> > 
> > We have not discussed this. Feel free to add to the wish list and 
> > propose an algorithm. We also need to discuss how best to implement the 
> > strategy pattern for decompositions in general, as there will often be 
> > multiple algorithms to choose from.
> I have plugged in the EigenvalueDecomposition class from JAMA, which 
> works fine for the PCA and CPCA modules. They do have a whole set of 
> decompositions, and they might be easy to implement in the package (if 
> they are free to be used).

Colt contains a port of much of JAMA, IIRC, and as Wolfgang posted not too long
ago, Colt's new license is much more compatible with the Apache license.  I'm
not sure if it's sufficiently compatible for us to start merging in code,


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