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MathGroup Archive 2013

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Unique QR decomposition

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131384] Unique QR decomposition
  • From: mpressprich at gmail.com
  • Date: Wed, 17 Jul 2013 01:49:23 -0400 (EDT)
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I am a Mathematica beginner.  I ran QRDecomposition on an invertible matrix and got negative diagonal elements in the R matrix.  How do I get Mathematica to return all positive diagonal elements for R?  According to Golub & Van Loan this should be possible and guarantees a unique solution.  (I naively assumed that Mathematica would do this automatically.)



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