r.out.mat(1grass) GRASS GIS User's Manual r.out.mat(1grass)
NAME
r.out.mat - Exports a GRASS raster to a binary MAT-File.
KEYWORDS
raster, export, output
SYNOPSIS
r.out.mat
r.out.mat --help
r.out.mat input=name output=name [--overwrite] [--help] [--verbose]
[--quiet] [--ui]
Flags:
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
input=name [required]
Name of input raster map
output=name [required]
Name for 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. At-
tributes such as map title and bounds will also be exported into addi-
tional 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 prob-
lems.
Everything should be Endian safe, so the resultant file can be simply
copied between different system architectures without binary transla-
tion.
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-preci-
sion floating point data should translate into NaN values as expected.
r.out.mat must load the entire map into memory before writing, there-
fore 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 informa-
tion stored in a single structured array.
SEE ALSO
r.in.mat
r.out.ascii, r.out.bin
r.null
The Octave project
AUTHOR
Hamish Bowman
Department of Marine Science
University of Otago
New Zealand
SOURCE CODE
Available at: r.out.mat source code (history)
Accessed: unknown
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GRASS 7.8.7 r.out.mat(1grass)
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