## maxima-bugs

 [Maxima-bugs] [ maxima-Bugs-3435971 ] eigenvectors produces wrong results From: SourceForge.net - 2011-11-10 08:02:44 ```Bugs item #3435971, was opened at 2011-11-10 00:02 Message generated for change (Tracker Item Submitted) made by You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3435971&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core - Solving equations Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: https://www.google.com/accounts () Assigned to: Nobody/Anonymous (nobody) Summary: eigenvectors produces wrong results Initial Comment: [vals,vec]:eigenvectors(matrix([0.2273,-0.0852],[-0.193,0.1794])); rat: replaced -0.0164436 by -1134/68963 = -0.01644360019141 rat: replaced 0.1794 by 897/5000 = 0.1794 rat: replaced 0.2273 by 2273/10000 = 0.2273 rat: replaced -0.01644360019141 by -1091/66348 = -0.01644360040996 rat: replaced 0.1794 by 897/5000 = 0.1794 rat: replaced 0.2273 by 2273/10000 = 0.2273 rat: replaced 1.2057635497678905E-12 by 1/829350000000 = 1.2057635497678905E-12 rat: replaced 2.1637741760636258E+11 by 216377417606/1 = 2.16377417606E+11 rat: replaced 2.1637741760636258E+11 by 216377417606/1 = 2.16377417606E+11 (%o40) [[[0.07289999842889,0.33380000157111],[1,1]],[[[1,1.812206572769953]],[[1, -1.25]]]] However, the eigenvectors should be [0.62166748, -0.78328126] and [0.46864735,0.88338534]. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3435971&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-3435971 ] eigenvectors produces wrong results From: SourceForge.net - 2012-08-16 16:06:01 ```Bugs item #3435971, was opened at 2011-11-10 00:02 Message generated for change (Comment added) made by rtoy You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3435971&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core - Solving equations Group: None >Status: Pending >Resolution: Invalid Priority: 5 Private: No Submitted By: https://www.google.com/accounts () Assigned to: Nobody/Anonymous (nobody) Summary: eigenvectors produces wrong results Initial Comment: [vals,vec]:eigenvectors(matrix([0.2273,-0.0852],[-0.193,0.1794])); rat: replaced -0.0164436 by -1134/68963 = -0.01644360019141 rat: replaced 0.1794 by 897/5000 = 0.1794 rat: replaced 0.2273 by 2273/10000 = 0.2273 rat: replaced -0.01644360019141 by -1091/66348 = -0.01644360040996 rat: replaced 0.1794 by 897/5000 = 0.1794 rat: replaced 0.2273 by 2273/10000 = 0.2273 rat: replaced 1.2057635497678905E-12 by 1/829350000000 = 1.2057635497678905E-12 rat: replaced 2.1637741760636258E+11 by 216377417606/1 = 2.16377417606E+11 rat: replaced 2.1637741760636258E+11 by 216377417606/1 = 2.16377417606E+11 (%o40) [[[0.07289999842889,0.33380000157111],[1,1]],[[[1,1.812206572769953]],[[1, -1.25]]]] However, the eigenvectors should be [0.62166748, -0.78328126] and [0.46864735,0.88338534]. ---------------------------------------------------------------------- >Comment By: Raymond Toy (rtoy) Date: 2012-08-16 09:06 Message: The eigenvalues computed by maxima are correct. A : matrix([0.2273,-0.0852],[-0.193,0.1794]); A . vec[1][1] - vals[1][1] * vec[1][1] -> matrix([0.0],[0.0]) A . vec[2][1] - vals[1][2] * vec[2][1] -> matrix([-0.2609],[-.4728046948356808]) You were probably expecting the eigenvectors to be normalized to unit length. Eigenvectors are unique only up to a scale factor. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3435971&group_id=4933 ```
 [Maxima-bugs] [ maxima-Bugs-3435971 ] eigenvectors produces wrong results From: SourceForge.net - 2012-09-21 05:47:59 ```Bugs item #3435971, was opened at 2011-11-10 00:02 Message generated for change (Settings changed) made by rtoy You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3435971&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core - Solving equations Group: None >Status: Closed Resolution: Invalid Priority: 5 Private: No Submitted By: https://www.google.com/accounts () Assigned to: Nobody/Anonymous (nobody) Summary: eigenvectors produces wrong results Initial Comment: [vals,vec]:eigenvectors(matrix([0.2273,-0.0852],[-0.193,0.1794])); rat: replaced -0.0164436 by -1134/68963 = -0.01644360019141 rat: replaced 0.1794 by 897/5000 = 0.1794 rat: replaced 0.2273 by 2273/10000 = 0.2273 rat: replaced -0.01644360019141 by -1091/66348 = -0.01644360040996 rat: replaced 0.1794 by 897/5000 = 0.1794 rat: replaced 0.2273 by 2273/10000 = 0.2273 rat: replaced 1.2057635497678905E-12 by 1/829350000000 = 1.2057635497678905E-12 rat: replaced 2.1637741760636258E+11 by 216377417606/1 = 2.16377417606E+11 rat: replaced 2.1637741760636258E+11 by 216377417606/1 = 2.16377417606E+11 (%o40) [[[0.07289999842889,0.33380000157111],[1,1]],[[[1,1.812206572769953]],[[1, -1.25]]]] However, the eigenvectors should be [0.62166748, -0.78328126] and [0.46864735,0.88338534]. ---------------------------------------------------------------------- Comment By: Raymond Toy (rtoy) Date: 2012-08-16 09:06 Message: The eigenvalues computed by maxima are correct. A : matrix([0.2273,-0.0852],[-0.193,0.1794]); A . vec[1][1] - vals[1][1] * vec[1][1] -> matrix([0.0],[0.0]) A . vec[2][1] - vals[1][2] * vec[2][1] -> matrix([-0.2609],[-.4728046948356808]) You were probably expecting the eigenvectors to be normalized to unit length. Eigenvectors are unique only up to a scale factor. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=3435971&group_id=4933 ```

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