NAME
r.sample.category - Create sampling points from each category in a raster map
KEYWORDS
raster,
sampling,
random,
points,
vector,
stratified sampling
SYNOPSIS
r.sample.category
r.sample.category --help
r.sample.category [-s] input=name output=name [sampled=name[,name,...]] npoints=integer[,integer,...] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -s
- If number of cells in category < npoints, skip category
- --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 with categories (classes)
- output=name [required]
- Name of output vector map with points at random locations
- sampled=name[,name,...]
- Names of input raster maps to be sampled
- npoints=integer[,integer,...] [required]
- Number of sampling points per category in the input map
- You can provide multiple numbers, one for each category in input raster (sorted ascending)
r.sample.category generates points at random locations.
Each category (class) in a raster map will contain specified number
of random points.
Different number of points can be specified for different categories.
For example, if there are categories 1, 4, 7 in the input raster map,
and npoints=100,200,300, 100 points will be generated in category 1,
200 points in category 4 and 300 points in category 7.
If only one number is specified, it will be used for every category.
Mask (
r.mask) to create points in areas
with each category, thus mask cannot be active when the module is used.
Categories are identified based on current computational region.
Generate three points at random location for each category (class)
in the raster map:
g.region raster=landclass96
r.sample.category input=landclass96 output=landclass_points npoints=3
Show the result:
d.rast map=landclass96
d.vect map=landclass_points icon=basic/circle fill_color=aqua color=blue size=10
Figure: Three random points in each category of landclass raster map
Create 2 random points per each category (class) in landclass96 raster
and sample elevation and geology_30m rasters at these points:
r.sample.category input=landclass96 output=landclass_points sampled=elevation,geology_30m npoints=2
Look at the created data:
v.db.select landclass_points sep=comma
The result of
v.db.select
is CSV table which can be used, for example in a spreadsheet application:
cat,landclass96,elevation,geology_30m
1,1,102.7855,270
2,1,105.78,270
3,2,114.5954,217
4,2,137.4816,921
5,3,71.19167,270
6,3,93.33904,270
7,4,76.41077,262
8,4,97.54424,217
9,5,138.455,405
10,5,88.8075,270
11,6,126.5298,217
12,6,86.73177,217
13,7,134.5381,217
14,7,99.6844,270
The module does not respect mask. More precisely it does not allow mask
to be active when it is started because it sets the mask by itself
for its own purposes. The mask is removed at the end of execution
but all other modules executed in parallel with this module (such
as rendering maps in GUI) will be influenced by the mask set
by this module.
v.sample,
r.random,
r.random.cells,
v.random,
v.what.rast,
r.describe
Vaclav Petras, NCSU OSGeoREL,
Anna Petrasova, NCSU OSGeoREL
Last changed: $Date: 2015-06-12 05:31:56 +0200 (Fri, 12 Jun 2015) $
SOURCE CODE
Available at: r.sample.category source code (history)
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GRASS Development Team,
GRASS GIS 7.4.1svn Reference Manual