Paolo: at a first glance I was persuaded you would perform exploratory analysis between two sets.<br><br>The same concepts expressed by Roger Bivand about mapping lattice matrices apply to scatterplots.<br><br>In case you would perform exploratory analysis on the data I suggest hexagon binning to make quick plots of one var versus another one. <br>
<br>Then you could add regression and/or LOWESS lines to the plot: look at:<br><a href="http://cran.r-project.org/web/packages/hexbin/index.html">http://cran.r-project.org/web/packages/hexbin/index.html</a><br><br>Enjoy!<br>
Duccio<br><br>------------------------------<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Message: 3<br>
Date: Wed, 22 Feb 2012 06:54:32 -0800 (PST)<br>
From: Roger Bivand <<a href="mailto:Roger.Bivand@nhh.no">Roger.Bivand@nhh.no</a>><br>
Subject: [GRASS-user] Re: spgrass6<br>
To: <a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a><br>
Message-ID: <<a href="mailto:1329922472770-4495201.post@n6.nabble.com">1329922472770-4495201.post@n6.nabble.com</a>><br>
Content-Type: text/plain; charset=us-ascii<br>
<br>
Just 2k may mean 4 million rectangles. R display is vector, hard-copy, with<br>
some recent support for raster grids when the rectangles are in fact square.<br>
As has been said, the graphics engine is not designed for fast screen<br>
output, but for scientific statistical graphics.<br>
<br>
spplot uses lattice graphics, which are slower anyway, but analytically more<br>
powerful. For me running levelplot() - the internals of spplot - on a 2k by<br>
2k matrix takes 2 seconds, but output to a png file using cairo takes 70<br>
seconds.<br>
<br>
Using the improved raster graphics handling for square cells with image()<br>
rather than spplot() and useRaster=TRUE - equivalent to<br>
image.SpatialGridDataFrame() and useRasterImage=TRUE with the same matrix<br>
takes 1.2 seconds on x11/cairo. You didn't say which version of R you are<br>
using - the raster graphics facilities have been improved recently.<br>
<br>
Did you try using image() instead of spplot() if your cells are square, and<br>
if rasterImage() is available in your version of R?<br>
<br>
Roger<br><br>
</blockquote></div>