Note: A new GRASS GIS stable version has been released: GRASS GIS 7. Go directly to the new manual page here
r.out.mat - Exports a GRASS raster to a binary MAT-File.
r.out.mat [-v] input=name output=string [--verbose] [--quiet]
- Verbose mode
- Verbose module output
- Quiet module output
- Name of input raster map
- Name for the output binary MAT-File
r.out.mat will export a GRASS raster map to a MAT-File which can
be loaded into Matlab or Octave for plotting or further analysis.
Attributes such as map title and bounds will also be exported into
additional array variables.
Specifically, the following array variables are created:
map_title (if it exists)
In addition, r.out.mat makes for a nice binary container format
for transferring georeferenced maps around, even if you don't use Matlab
r.out.mat exports a Version 4 MAT-File. These files should
successfully load into more modern versions of Matlab and Octave
without any problems.
Everything should be Endian safe, so the resultant file can be simply
copied between different system architectures without binary translation.
As there is no IEEE value for NaN for integer maps, GRASS's null
value is used to represent it within these maps. You'll have to do something
like this to clean them once the map is loaded into Matlab:
map_data(find(map_data < -1e9)) = NaN;
Null values in maps containing either floating point or double-precision
floating point data should translate into NaN values as expected.
r.out.mat must load the entire map into memory before writing,
therefore it might have problems with huge maps.
(a 3000x4000 DCELL map uses about 100mb RAM)
GRASS defines its map bounds at the outer-edge of the bounding cells, not at
the coordinates of their centroids. Thus, the following Matlab commands may
be used to determine the map's resolution information:
[rows cols] = size(map_data)
x_range = map_eastern_edge - map_western_edge
y_range = map_northern_edge - map_southern_edge
ns_res = y_range/rows
ew_res = x_range/cols
In Matlab, plot with either:
imagesc(map_data), axis equal, axis tight, colorbar
contourf(map_data, 24), axis ij, axis equal, axis tight, colorbar
Add support for exporting map history, category information, color map, etc.
Option to export as a version 5 MAT-File, with map and support information
stored in a single structured array.
The Octave project
Department of Marine Science
University of Otago
Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $
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