Ted Dunning wrote: > Numerical issues should not impinge on a computation this small. > > For reference, I replicated your computation and found reasonable > eigenvalues and vectors: > >> m = matrix(c(0,1,-1,1,1,0,-1,0,1), nrow=3) >> m > [,1] [,2] [,3] > [1,] 0 1 -1 > [2,] 1 1 0 > [3,] -1 0 1 >> eig(m) > Error: could not find function "eig" >> eigen(m) > $values > [1] 2 1 -1 > > $vectors > [,1] [,2] [,3] > [1,] 0.5773503 0.0000000 0.8164966 > [2,] 0.5773503 0.7071068 -0.4082483 > [3,] -0.5773503 0.7071068 0.4082483 > > > Your usage appears to be in accord with the suggested usage, but have you > tried it with a tolerance of, say, 1e-3? > > On Sat, Sep 19, 2009 at 10:41 PM, Axel <axel...@gmail.com> wrote: > >> Hello >> >> I'm trying to calculate the Eigenvectors of this Wikipedia example: >> http://en.wikipedia.org/wiki/Eigenvalue_algorithm#Identifying_eigenvectors >> >> with this JUnit method: >> >> public void testEigenDecomposition() { >> double[][] m = { { 0.0, 1.0, -1.0 }, { 1.0, 1.0, 0.0 }, { -1.0, >> 0.0, 1.0 } }; >> RealMatrix rm = new Array2DRowRealMatrix(m); >> assertEquals(rm.toString(), >> >> "Array2DRowRealMatrix{{0.0,1.0,-1.0},{1.0,1.0,0.0},{-1.0,0.0,1.0}}"); >> EigenDecompositionImpl ed = new EigenDecompositionImpl(rm, >> MathUtils.SAFE_MIN); >> RealVector rv0 = ed.getEigenvector(0); >> assertEquals(rv0.toString(), "{(NaN); (NaN); (NaN)}"); >> } >> >> but I'm getting only {(NaN); (NaN); (NaN)} as a result vector. >> >> Is this intentionally (because of numerical inaccuracy?) or am I doing >> something wrong in using EigenDecompositionImpl? >> >> -- >> Axel Kramer >> http://code.google.com/p/symja >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >> For additional commands, e-mail: dev-h...@commons.apache.org >> >> > > Thanks for reporting this. Looks like a bug. The eigenvalues are being correctly computed but all three eigenvectors are coming out <NaN, NaN, NaN>
This is being tracked as MATH-297. Phil --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
