NAME¶
r.out.mat - Exports a GRASS raster to a binary MAT-File.
KEYWORDS¶
raster, export
SYNOPSIS¶
r.out.mat
r.out.mat help
r.out.mat [-
v]
input=
name
output=
string [--
verbose] [--
quiet]
Flags:¶
- -v
-
Verbose mode
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
Parameters:¶
- input=name
-
Name of input raster map
- output=string
-
Name for the output binary MAT-File
DESCRIPTION¶
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_data map_name map_title (if it exists)
map_northern_edge map_southern_edge map_eastern_edge
map_western_edge
In addition,
r.out.mat makes for a nice binary container format for
transferring georeferenced maps around, even if you don't use Matlab or
Octave.
NOTES¶
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:
Null values in maps containing either floating point or double-precision
floating point data should translate into <tt>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
EXAMPLE¶
In Matlab, plot with either:
imagesc(map_data), axis equal, axis tight, colorbar
or
contourf(map_data, 24), axis ij, axis equal, axis tight, colorbar
TODO¶
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.
SEE ALSO¶
r.in.mat
r.out.bin
r.null
The Octave project
AUTHOR¶
Hamish Bowman
Department of Marine Science
University of Otago
New Zealand
Last changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $
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