Skip to content

r.li.patchdensity

Calculates patch density index on a raster map, using a 4 neighbour algorithm

r.li.patchdensity input=name config=name output=name [--overwrite] [--verbose] [--quiet] [--qq] [--ui]

Example:

r.li.patchdensity input=name config=name output=name

grass.script.run_command("r.li.patchdensity", input, config, output, overwrite=None, verbose=None, quiet=None, superquiet=None)

Example:

gs.run_command("r.li.patchdensity", input="name", config="name", output="name")

grass.tools.Tools.r_li_patchdensity(input, config, output, overwrite=None, verbose=None, quiet=None, superquiet=None)

Example:

tools = Tools()
tools.r_li_patchdensity(input="name", config="name", output="name")

This grass.tools API is experimental in version 8.5 and expected to be stable in version 8.6.

Parameters

input=name [required]
    Name of input raster map
config=name [required]
    Configuration file
output=name [required]
    Name for output raster map
--overwrite
    Allow output files to overwrite existing files
--help
    Print usage summary
--verbose
    Verbose module output
--quiet
    Quiet module output
--qq
    Very quiet module output
--ui
    Force launching GUI dialog

input : str, required
    Name of input raster map
    Used as: input, raster, name
config : str, required
    Configuration file
    Used as: input, file, name
output : str, required
    Name for output raster map
    Used as: output, raster, name
overwrite : bool, optional
    Allow output files to overwrite existing files
    Default: None
verbose : bool, optional
    Verbose module output
    Default: None
quiet : bool, optional
    Quiet module output
    Default: None
superquiet : bool, optional
    Very quiet module output
    Default: None

input : str | np.ndarray, required
    Name of input raster map
    Used as: input, raster, name
config : str | io.StringIO, required
    Configuration file
    Used as: input, file, name
output : str | type(np.ndarray) | type(np.array) | type(gs.array.array), required
    Name for output raster map
    Used as: output, raster, name
overwrite : bool, optional
    Allow output files to overwrite existing files
    Default: None
verbose : bool, optional
    Verbose module output
    Default: None
quiet : bool, optional
    Quiet module output
    Default: None
superquiet : bool, optional
    Very quiet module output
    Default: None

Returns:

result : grass.tools.support.ToolResult | np.ndarray | tuple[np.ndarray] | None
If the tool produces text as standard output, a ToolResult object will be returned. Otherwise, None will be returned. If an array type (e.g., np.ndarray) is used for one of the raster outputs, the result will be an array and will have the shape corresponding to the computational region. If an array type is used for more than one raster output, the result will be a tuple of arrays.

DESCRIPTION

r.li.patchdensity calculates the "patch density index", the number of patches per square kilometer, as:

PD = Npatch / A

with:

  • A:sampling area size
  • Npatch: number of patches

This index is calculated using a 4 neighbour algorithm, diagonal cells are ignored when tracing a patch.

NOTES

Do not use absolute path names for the config and output file/map parameters. If the "moving window" method was selected in g.gui.rlisetup, then the output will be a raster map, otherwise an ASCII file will be generated in the folder C:\Users\userxy\AppData\Roaming\GRASS8\r.li\output\ (MS-Windows) or $HOME/.grass8/r.li/output/ (GNU/Linux).

A sample area of only NULL values is considered to have zero patches, that is, the result is always ≥ 0.

EXAMPLES

To calculate patch density index on map my_map, using my_conf configuration file (previously defined with g.gui.rlisetup) and saving results in my_out, run:

r.li.patchdensity input=my_map conf=my_conf output=my_out

Example for Spearfish forest areas:

g.region raster=landcover.30m -p
# extract forested areas:
r.category landcover.30m
r.mapcalc "forests = if(landcover.30m >= 41 && landcover.30m <= 43, 1, null())"

# patch density (7x7 moving window defined in g.gui.rlisetup):
r.li.patchdensity forests conf=movwindow7 out=forests_p_dens7
r.univar forests_p_dens7
d.rast.leg forests_p_dens7

r.to.vect forests out=forests feature=area
d.vect forests type=boundary

Forest map (North Carolina sample dataset) example:

g.region raster=landclass96 -p
r.mapcalc "forests = if(landclass96 == 5, 1, null() )"
r.li.patchdensity input=forests conf=movwindow7 out=forests_patchdensity_mov7

# verify
r.univar forests_patchdensity_mov7
r.to.vect input=forests output=forests type=area
d.mon wx0
d.rast forests_patchdensity_mov7
d.vect forests type=boundary

SEE ALSO

r.li (package overview), g.gui.rlisetup

REFERENCES

McGarigal, K., and B. J. Marks. 1995. FRAGSTATS: spatial pattern analysis program for quantifying landscape structure. USDA For. Serv. Gen. Tech. Rep. PNW-351. (PDF)

AUTHORS

Michael Shapiro - CERL (patch identification)
Markus Metz (statistics)

SOURCE CODE

Available at: r.li.patchdensity source code (history)
Latest change: Tuesday Apr 29 06:19:47 2025 in commit 12f893b