Re: [eigen] Column matrix |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Column matrix*From*: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>*Date*: Thu, 5 Nov 2009 14:39:29 +0100*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=WpC7MZlj8paQ/j0x8FrOX43dGv8QPDsgpaRJzEyFiAo=; b=w1zZCTa+WahHsicbgO4bPjIRgFagmlmXqxl58AZ0JUyvG+66ZyEbTUmJHzJFXndJeb K3TO+7cIB8RddmX3dA609lplJJYh3ojF+q3Q+7WQ8n7lsTWVwFqHlFG7z7pmL1GGIDtd Y+BhQGsl99yjcUVEhSTjxTX1ReX8pAbO8ghfg=*Domainkey-signature*: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=wU/wVMyREwqQOiNhLdT5UF6MLzCVcHTiDxJW0Yqh8F9fek6qGjE5BZATT5pnRmNuQM hc6VGqjaNi3+++cAlo9gNfNaSbITwElx6rG47qmRk34+nfCxHGxEWKRraSTCAKerLqEW S303i3a5J7RBExPMT3vMU5+62hV7exfANqSVc=

Hi,

On Wed, Nov 4, 2009 at 2:56 PM, guillaume saupin <guillaume.saupin@xxxxxx> wrote:

I'm not sure to fully understand what you need here, but what I'm sure about, is that's not in Eigen ;)

So, you're looking for an efficient representation for matrices having a couple of columns which are "empty", right ? So, e.g., if you have a n x m matrix with k non null columns, I guess you would store it into a n x k dense (or sparse) matrix, plus a vector of k integers storing the real column index of each column. If so, then a question is do we really need a new type of matrix for that ? I mean, isn't it enough to simply remove those columns from your problem ? Perhaps I'm missing something though ?

gael.

Hello,

Is there a kind of sparse matrix in eigen which stores only the non null column of a matrix (i.e. a ColumnMatrix) ?

I'm not sure to fully understand what you need here, but what I'm sure about, is that's not in Eigen ;)

So, you're looking for an efficient representation for matrices having a couple of columns which are "empty", right ? So, e.g., if you have a n x m matrix with k non null columns, I guess you would store it into a n x k dense (or sparse) matrix, plus a vector of k integers storing the real column index of each column. If so, then a question is do we really need a new type of matrix for that ? I mean, isn't it enough to simply remove those columns from your problem ? Perhaps I'm missing something though ?

gael.

In our libraries, we currently use this kind of matrix and as we plan to completely rely on Eigen, we'd like to have this kind of matrix.

As for the SkylineMatrix, we are willing to develop this ColumnMatrix if it does not already exists, and if you are ready to integrate it inside eigen..

Thanks,

guillaume

**Follow-Ups**:**Re: [eigen] Column matrix***From:*guillaume saupin

**References**:**[eigen] Column matrix***From:*guillaume saupin

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