Re: [eigen] Error: trying to recover Q matrix in sparse QR factorization |

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*To*: eigen <eigen@xxxxxxxxxxxxxxxxxxx>*Subject*: Re: [eigen] Error: trying to recover Q matrix in sparse QR factorization*From*: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>*Date*: Tue, 7 May 2013 15:36:16 +0200*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:mime-version:in-reply-to:references:from:date:message-id :subject:to:content-type:content-transfer-encoding; bh=3IvO2L8oVDHkerP8FJEdSN/5zTaDPRDiGjhgWxi1QxQ=; b=rnLsvurot/ZFWMQpQZORyQN1gz++QETLuzX9FleVoZd5dNhfijlb96J5/MGd1jdrKo 9/scQR57bAUjEgsKoxiceN1TupE1gWiOyjSNHScvd8CaYAmj9F/jcfOytA9T1bXGJ4O9 OrroURFMZwKMw47+3CZLLVBvkoHqODijjghCItmdS98Rv3a1ruZvENgg2yUa5jeOUq5D MXr6Jld5jt6AWOnNdlmPEbdLspHp/WXXYX3PTu+HX3d8V+vs32H+xZToqW6Gv002hcms S7BXLHWd8js9NX4FA3rFgXNerk5PljuPx6BpGv9b7XU0RjdRZxBx3ITD1/GLB2OXfKam 4k9g==

Need to be fixed: http://eigen.tuxfamily.org/bz/show_bug.cgi?id=596 In the meantime, multiplying by the identity matrix is the way to go. gael On Tue, May 7, 2013 at 2:58 PM, Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx> wrote: > On 07.05.2013 05:03, Avneesh Saluja wrote: >> >> Hello, >> >> I have a question regarding the sparse QR implementation in the latest >> development build of Eigen. >> >> I would like to recover the Q matrix after the factorization, but can't >> quite do so. I have followed the suggestion in the following link to get >> the SparseMatrix representation of Q (where I assume A is the original >> matrix that we are taking the factorization of): >> >> http://eigen.tuxfamily.org/dox-devel/classEigen_1_1SparseQR.html#ac27067ab301641fe6cc35c216a9b18a2 > > > That looks mostly like a documentation issue. In general, it does not make > sense to store Q as a sparse matrix, since usually it is not anything near > sparse. You can directly use qr_factorizer.matrixQ() inside expressions. If > you really need the actual Q, I guess the simplest way would be to multiply > by an identity matrix. > > > Christoph > > > -- > ---------------------------------------------- > Dipl.-Inf., Dipl.-Math. Christoph Hertzberg > Cartesium 0.049 > Universität Bremen > Enrique-Schmidt-Straße 5 > 28359 Bremen > > Tel: +49 (421) 218-64252 > ---------------------------------------------- > >

**Follow-Ups**:**Re: [eigen] Error: trying to recover Q matrix in sparse QR factorization***From:*Avneesh Saluja

**References**:**[eigen] Error: trying to recover Q matrix in sparse QR factorization***From:*Avneesh Saluja

**Re: [eigen] Error: trying to recover Q matrix in sparse QR factorization***From:*Christoph Hertzberg

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