Re: [eigen] Column matrix |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Column matrix*From*: guillaume saupin <guillaume.saupin@xxxxxx>*Date*: Thu, 05 Nov 2009 15:22:14 +0100

Gael Guennebaud wrote:

Hi,On Wed, Nov 4, 2009 at 2:56 PM, guillaume saupin<guillaume.saupin@xxxxxx <mailto:guillaume.saupin@xxxxxx>> wrote: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 sureabout, is that's not in Eigen ;)So, you're looking for an efficient representation for matrices havinga couple of columns which are "empty", right ? So, e.g., if you have an x m matrix with k non null columns, I guess you would store it intoa n x k dense (or sparse) matrix, plus a vector of k integers storingthe real column index of each column.

If so, then a question is do we really need a new type of matrix forthat ? I mean, isn't it enough to simply remove those columns fromyour 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

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

**Re: [eigen] Column matrix***From:*Gael Guennebaud

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