v.rast.stats(1grass) GRASS GIS User's Manual v.rast.stats(1grass)
NAME
v.rast.stats - Calculates univariate statistics from a raster map
based on a vector map and uploads statistics to new attribute columns.
KEYWORDS
vector, statistics, raster, univariate statistics, zonal statistics,
sampling, querying
SYNOPSIS
v.rast.stats
v.rast.stats --help
v.rast.stats [-cd] map=name [layer=string] [where=sql_query]
raster=name[,name,...] column_prefix=string[,string,...]
[method=string[,string,...]] [percentile=integer] [--help] [--ver-
bose] [--quiet] [--ui]
Flags:
-c
Continue if upload column(s) already exist
-d
Create densified lines (default: thin lines)
All cells touched by the line will be set, not only those on the
render path
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
map=name [required]
Name of vector map
Or data source for direct OGR access
layer=string
Layer number or name
Vector features can have category values in different layers. This
number determines which layer to use. When used with direct OGR ac-
cess this is the layer name.
Default: 1
where=sql_query
WHERE conditions of SQL statement without ’where’ keyword
Example: income < 1000 and population >= 10000
raster=name[,name,...] [required]
Name of input raster map to calculate statistics from
column_prefix=string[,string,...] [required]
Column prefix for new attribute columns
method=string[,string,...]
The methods to use
Options: number, null_cells, minimum, maximum, range, average, std-
dev, variance, coeff_var, sum, first_quartile, median, third_quar-
tile, percentile
Default: number,null_cells,minimum,maximum,range,average,std-
dev,variance,coeff_var,sum,first_quartile,median,third_quar-
tile,percentile
percentile=integer
Percentile to calculate
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 uni-
variate statistics are calculated per vector category (cat) from the
raster map and the results uploaded to the vector map attribute table.
A new column is generated in the attribute table for each statistic re-
quested in method (if not already present).
The univariate statistics include the number of raster cells counted,
the number of raster NULL cells counted, minimum and maximum cell val-
ues, range, average, standard deviation, variance, coefficient of vari-
ation, sum, first quartile, median, third quartile, and percentile.
NOTES
v.rast.stats is only meaningful for lines or polygons.
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 ad-
ditional 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 extended statistics
(first_quartile,median,third_quartile,percentile ) are being requested
with a very large region setting. If the region is too large the module
should display memory allocation errors. Basic statistics can be calcu-
lated using any size input region.
EXAMPLES
Example to upload DEM statistics to ZIP codes vector map (North Car-
olina sample dataset):
g.copy vect=zipcodes_wake,myzipcodes_wake
# set computational region to DEM:
g.region raster=elevation -p
# calculate selected DEM statistics, upload to vector map table:
v.rast.stats myzipcodes_wake raster=elevation \
column_prefix=elev method=minimum,maximum,average,range,stddev,percentile \
percentile=95
# 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.vect.stats, v.what.rast, v.what.rast3,
v.what.vect
AUTHOR
Markus Neteler, CEA (for the EDEN EU/FP6 Project)
SOURCE CODE
Available at: v.rast.stats source code (history)
Accessed: unknown
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GRASS 7.8.7 v.rast.stats(1grass)
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