[Matplotlib-users] Re:

[Dominique O. <Dom...@po...>]

> To: Nils Wagner <nw...@me...>
> Cc: SciPy Users List <sci...@sc...>,
> 	mat...@li...
> Subject: Re: [Matplotlib-users] Visualizing Sparsity Pattern of matrices
> From: John Hunter <jdh...@ac...>
> Date: Thu, 11 Nov 2004 09:16:03 -0600
> 
> 
>>>>>>"Nils" == Nils Wagner <nw...@me...> writes:
> 
> 
>     Nils> Hi all, Structure plots provide a quick visual check on the
>     Nils> sparsity pattern of the matrix.  A structure plot is a
>     Nils> rectangular array of dots; a dot is black if the
>     Nils> corresponding matrix element is nonzero otherwise it is
>     Nils> white.
> 
>     Nils> Is it possible to generate such plots with scipy or should
>     Nils> we switch over to matplotlib ?
> 
> Here's another implementation that uses images - likely to be much
> faster for very large matrices.

Hi,

As part of a programming environment for optimization in Python (soon to 
be released hopefully), I use Matplotlib for the graphics. I created 
several functions imitating Matlab's spy() using scatter(). My sparse 
matrices are represented in linked-list, compressed column or compressed 
row storage using the PySparse implementation
	http://people.web.psi.ch/geus/pyfemax/pysparse.html

Using scatter, I can plot the sparsity pattern of matrices with several 
thousands of lines and columns in a blink on my 1.7GHz P4 laptop. Using 
color maps, you can even color your dots according to the magnitude of 
the element they represent (a 2-dimensional "city plot" of a matrix).

Dominique