NAME¶
v.rast.stats - Calculates univariate statistics from a raster map
based on vector polygons and uploads statistics to new attribute columns.
KEYWORDS¶
vector, raster, statistics
SYNOPSIS¶
v.rast.stats
v.rast.stats help
v.rast.stats [-
ce]
vector=
name
[
layer=
integer]
raster=
name
colprefix=
string [
percentile=
integer]
[--
verbose] [--
quiet]
Flags:¶
- -c
-
Continue if upload column(s) already exist
- -e
-
Calculate extended statistics
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
Parameters:¶
- vector=name
-
Name of vector polygon map
- layer=integer
-
A single vector map can be connected to multiple database tables. This
number determines which table to use
Default: 1
- raster=name
-
Name of raster map to calculate statistics from
- colprefix=string
-
Column prefix for new attribute columns
- percentile=integer
-
Percentile to calculate (requires extended statistics flag)
Options: 0-100
Default: 90
DESCRIPTION¶
v.rast.stats calculates basic univariate statistics from a raster map
only for the parts covered by the specified vector map. The vector map will be
rasterized according to the raster map resolution. Then univariate statistics
are calculated per vector category (cat) from the raster map and the results
uploaded to the vector map attribute table. New columns are generated in the
attribute table if not already present.
Nine columns are generated (n, min, max, range, mean, stddev, variance,
coeff_var, sum) according to the output of
r.univar. If the
-e
extended statistics flag is given the 1st quartile, median, 3rd quartile, and
given percentile are also calculated.
NOTES¶
The module may take a long time to run if the raster region contains a large
number of cells. In this case the
--verbose flag may be used to track
progress.
The script stops if a (prefixed) upload column is already present in the vector
map attribute table, unless otherwise instructed with the
-c continue
flag. The column prefix will be separated from the statistic name with an
underscore. For example with a prefix of "elev" the sum column will
be named elev_sum.
If a DBF database is being used, note that column names are restricted by the
DBF specification to 10 characters. Therefore it is advised to be economical
in the use of the column prefix when using DBF as any additional characters
will be chopped off.
If a MASK is present, it will be restored after the script finished. The script
changes temporarily to the resolution of the given raster map.
Large amounts of system memory can be used when the
-e extended
statistics flag is used with a very large region setting. If the region is too
large the module should display memory allocation errors. Basic statistics can
be calculated using any size input region.
EXAMPLES¶
Example to upload DEM statistics to ZIP codes vector map (North Carolina sample
dataset):
g.copy vect=zipcodes_wake,myzipcodes_wake
# set computational region to DEM:
g.region rast=elevation -p
# calculate DEM statistics, upload to vector map table:
v.rast.stats myzipcodes_wake raster=elevation colprefix=elev
# verify results:
v.info -c myzipcodes_wake
v.db.select myzipcodes_wake
v.univar myzipcodes_wake column=elev_range type=centroid
SEE ALSO¶
r.univar, v.univar, v.what.rast, v.what.vect
AUTHOR¶
Markus Neteler, CEA (for the EDEN EU/FP6 Project)
Last changed: $Date: 2011-11-08 10:42:51 +0100 (Tue, 08 Nov 2011) $
Full index
© 2003-2014 GRASS Development Team