Hi Andrea, that's exactly what we are looking for, so do not hesitate to ask questions.
Thomas On Tue, Nov 12, 2013 at 11:54 AM, andrea antonello < andrea.antone...@gmail.com> wrote: > Hi Thomas, > > > good to hear. > > Sounds like an interesting problem you are working on. > > If you have found a good solution feel free to come back to use, we might > > want to include it in our user guide how an EigenDecomposition could be > > used. > > thanks for pointing this out, I was a bit afraid to go offtopic. > But I would be happy to share a small eigenvector real world example > if there is interest. I will try to put together something on an > accessible wiki page, but I might need some help to finish it for > proper use in documentation :) > > I'll keep you posted. > Thanks, > Andrea > > > > > Thanks, > > > > Thomas > > > > > > > > On Tue, Nov 12, 2013 at 11:31 AM, andrea antonello < > > andrea.antone...@gmail.com> wrote: > > > >> Hi Thomas, > >> you are definitely right. I was fooled by the "nice" result of the > >> JAMA calculation, not noticing that it is there that I was extracting > >> values in a strange order. > >> > >> I now made some 3x3 tests on known results and also with the A * v = > >> lambda * v constraint and everything is alright. > >> > >> I still have to figure out how to properly use the results to split > >> higher elevation parts from lower z parts in a x,y,z dataset, but the > >> eigenvectors and values are in the right place now. > >> > >> Thanks, > >> Andrea > >> > >> > >> > >> > >> On Mon, Nov 11, 2013 at 1:21 PM, Thomas Neidhart > >> <thomas.neidh...@gmail.com> wrote: > >> > On 11/11/2013 11:40 AM, andrea antonello wrote: > >> >> Hi Thomas, > >> >> thanks for your reply. > >> >> > >> >>> the result of CM and jama are identical, the difference is just in > the > >> >>> way how the data is stored. > >> >>> > >> >>> Afaik in jama calling getV() returns a vector in row format whereas > in > >> >>> CM the are stored in column format. > >> >>> > >> >>> If you transpose the matrix (or call getVT()) you will see that the > >> >>> vectors are identical, except for the signs and order. The reason > for > >> >>> this is that for CM the eigenvalues/eigenvectors are sorted in > >> >>> descending order in case of a symmetric matrix, which is the case > for > >> >>> your matrix. > >> >> > >> >> the problems is that the result is not just different in the > >> >> transposed way. And in fact if I pick the getVT,results are still not > >> >> the same. > >> >> The result seems to be reflected on the secondary diagonal, not the > >> >> primary diagonal. > >> >> > >> >> Furthermore, if I use the API, I do not expect to be problems of rows > >> >> and columns, so if I use: > >> >> > >> >> double eigenValue = eigenDecomposition.getRealEigenvalue(i); > >> >> RealVector eigenVector = eigenDecomposition.getEigenvector(i); > >> >> > >> >> I expect the eigenvector and eigenvalue to be the right ones for the > >> >> given index, no matter how the results are given in the matrixes. > >> >> > >> >> But the results I get are, for the same eigenvalue: > >> >> CM: eigenVal: 0.8056498828134406, eigenVect: [0.9015723557614027, > >> >> 0.19005937823202243, 0.38864472217295326 > >> >> JAMA: eigenVal: 0.8056498828134406, eigenVect: [-0.7731388420716028, > >> >> 0.5012101463530931, -0.38864472217295326] > >> >> > >> >> I am still quite puzzled about what I am missing. > >> > > >> > I do not know how you get the eigenvector from jama, as there is no > >> > getEigenVector method. > >> > > >> > The class javadoc of their EigenvalueDecomposition states: > >> > > >> > columns of V represent the eigenvectors in the sense that A*V = > V*D, > >> > i.e. A.times(V) equals V.times(D). The matrix V may be badly > >> > conditioned, or even singular, so the validity of the equation > >> > A = V*D*inverse(V) depends upon V.cond(). > >> > > >> > Looking at your example it looks like you took the rows of V to > extract > >> > your eigenvector. > >> > > >> > You can also easily verify if your eigenvector is correct: > >> > > >> > A * v = lambda * v > >> > > >> > Thomas > >> > > >> > --------------------------------------------------------------------- > >> > To unsubscribe, e-mail: user-unsubscr...@commons.apache.org > >> > For additional commands, e-mail: user-h...@commons.apache.org > >> > > >> > >> --------------------------------------------------------------------- > >> To unsubscribe, e-mail: user-unsubscr...@commons.apache.org > >> For additional commands, e-mail: user-h...@commons.apache.org > >> > >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: user-unsubscr...@commons.apache.org > For additional commands, e-mail: user-h...@commons.apache.org > >
