java jama array problem

Question

I asked a question before but duffymo said it is not clear so i am going to post it again here. I am using Jama api for SVD calculation. I know very well about jama and SVD. Jama does not work if your column are more than rows. I have this situation. What should I do?? any help? I can't transpose the matrix too as it can produce wrong results. Thanks.

P.S: I am calculating LSI with the help of jama. I am going like column(docs) and rows ( terms )

Usually if your question is unclear, you can edit the original question besides posting a new one — Anthony Forloney, Jan 30 '10 at 20:17
And even if you have a valid reason to post a new version of another question, it's nice to link to the original so we can read the comments there and see what the difference is this time. — Mark Byers, Jan 30 '10 at 20:19

score 1 · Answer 1 · edited Feb 07 '13 at 19:59

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If I understand correctly you are trying to compute the SVD of a matrix which is not square, and you have the library JAMA which only works on square matrices? If I have understood you correctly then the answer to your question is obvious: Get a library which does compute SVD for non-square matrices. If I remember correctly Numerical Recipes contains such an algorithm, I expect you can find many other sources with Google.

edited Feb 07 '13 at 19:59

user229044

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answered Jan 31 '10 at 04:17

High Performance Mark

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Hi, Thanks for your reply. Yes you understand my problem 100% correctly. I couldn't find any good java API for SVD. can you please tell me one??? also jama is veyr slow it took 2 hours to calculate SVD on 500 column matrix – user238384 Jan 31 '10 at 17:13

score 1 · Answer 2 · answered Feb 27 '10 at 17:31

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Why not use transpose? If X = USV', then X' = VS'U'. Right?

Transpose your matrix. Get U, S and V. Transpose everything back.

answered Feb 27 '10 at 17:31

Ahmed Abdelkader

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for LSI it should be term by document so you can not transpose – user238384 Feb 27 '10 at 20:56

score 0 · Answer 3 · answered Apr 29 '10 at 07:02

Since you're doing LSI, you could use SVDLIBJ, which is the Java equivalent of SVDLIBC, which is one of the most scalable SVD implementations that is freely available. The S-Space package has a command-line tool for SVDLIBJ set up already. Also, you can use their Matrix libraries and avoid the command-line if that fits your needs better.

score 0 · Answer 4 · answered Feb 13 '12 at 06:53

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I now it is a really late reply . But i thought it is better late than never

But i am aware that jblas performs svd in a effective manner.

answered Feb 13 '12 at 06:53

CTsiddharth

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java jama array problem

4 Answers4