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Axel Kramer edited comment on MATH-320 at 12/31/09 12:02 PM: ------------------------------------------------------------- This statement should print the values of the original matrix approximately: {code:java} System.out.println(svd.getU().multiply(svd.getS()).multiply(svd.getVT())); {code} This is true for {code:java} public void testMath320A() { {code} but not for {code:java} public void testMath320B() { {code} For reference values try wolfram alpha: N[SingularValueDecomposition[{{1,2},{1,2}}]] was (Author: axelclk): This statement should print the values of the original matrix approximately: {code:java} System.out.println(svd.getU().multiply(svd.getS()).multiply(svd.getVT())); {code} This is true for {code:java} public void testMath320A() { {code} but not for {code:java} public void testMath320B() { {code} For reference valus try wolfram alpha: N[SingularValueDecomposition[{{1,2},{1,2}}]] > NaN singular value from SVD > --------------------------- > > Key: MATH-320 > URL: https://issues.apache.org/jira/browse/MATH-320 > Project: Commons Math > Issue Type: Bug > Affects Versions: 2.0 > Environment: Linux (Ubuntu 9.10) java version "1.6.0_16" > Reporter: Dieter Vandenbussche > > The following jython code > Start code > from org.apache.commons.math.linear import * > > Alist = [[1.0, 2.0, 3.0],[2.0,3.0,4.0],[3.0,5.0,7.0]] > > A = Array2DRowRealMatrix(Alist) > > decomp = SingularValueDecompositionImpl(A) > > print decomp.getSingularValues() > End code > prints > array('d', [11.218599757513008, 0.3781791648535976, nan]) > The last singular value should be something very close to 0 since the matrix > is rank deficient. When i use the result from getSolver() to solve a system, > i end > up with a bunch of NaNs in the solution. I assumed i would get back a least > squares solution. > Does this SVD implementation require that the matrix be full rank? If so, > then i would expect > an exception to be thrown from the constructor or one of the methods. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.