[R-sig-Geo] importing GRIDs from ArcView or ASCII rasters

[Roger Bivand]

On Wed, 28 Dec 2005, Carlos Alberto Arnillas wrote:

> Hello
> I am trying to import a set of raster files (in grid format, supported
> by Arc View 3.x) to make some logistic regressions. I did a small
> program to import them from a ASCII format, but it's too slow.
> I'm not working with GRASS, do you have any idea about how can I do
> that?

Which format are the data stored in? Arc ASCII grid is much the easiest, 
and the maptools package provides functions for reading and writing these:

?readAsciiGrid

gives the details, and can be used easily on any platform. Other formats 
can be read through rgdal, but this depends on external software, so is 
easiest on Unix/Linux, where users can readily build GDAL and PROJ.4 from 
source first. If you need to use geotiffs, for example (and if ArcView can 
write them), rgdal would solve your problem. You may need to think things 
through first if your rasters are large and if there are many missing 
values - the sp SpatialGrid and SpatialPixels classes may be helpful.

> Thanks,
> 
> Carlos Alberto
> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no