r.pi.index

Basic patch based indices

Command linePython (grass.script)

r.pi.index [-a] input=name output=name keyval=integer method=string [title="phrase"] [--overwrite] [--verbose] [--quiet] [--qq] [--ui]

Example:

r.pi.index input=name output=name keyval=integer method=string

grass.script.run_command("r.pi.index", input, output, keyval, method, title=None, flags=None, overwrite=False, verbose=False, quiet=False, superquiet=False)

Example:

gs.run_command("r.pi.index", input="name", output="name", keyval=integer, method="string")

Parameters

Command linePython (grass.script)

input=name [required]
    Raster map containing categories
output=name [required]
    Output patch-based result as raster map
keyval=integer [required]
    The value of the class to be analysed
method=string [required]
    Operation to perform on fragments
    Allowed values: area, perimeter, shape, border, compactness, asymmetry, area-perimeter, fractal, ENN
title="phrase"
    Title for resultant raster map
-a
    Set for 8 cell-neighbors. 4 cell-neighbors are default
--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
    Raster map containing categories
    Used as: input, raster, name
output : str, required
    Output patch-based result as raster map
    Used as: output, raster, name
keyval : int, required
    The value of the class to be analysed
method : str, required
    Operation to perform on fragments
    Allowed values: area, perimeter, shape, border, compactness, asymmetry, area-perimeter, fractal, ENN
title : str, optional
    Title for resultant raster map
    Used as: "phrase"
flags : str, optional
    Allowed values: a
    a
        Set for 8 cell-neighbors. 4 cell-neighbors are default
overwrite: bool, optional
    Allow output files to overwrite existing files
    Default: False
verbose: bool, optional
    Verbose module output
    Default: False
quiet: bool, optional
    Quiet module output
    Default: False
superquiet: bool, optional
    Very quiet module output
    Default: False

DESCRIPTION

r.pi.index is a patch based fragmentation analysis package. Computation of basic fragmentation indices can be accomplished.

Available options for the index to be computed for patches within a certain class are: area (area), perimeter (perim), SHAPE (shape), Border-Index (bor), Compactness (comp), Asymmetry (asym), area-perimeter ratio (apr), fractal dimension (fract), distance to euclidean nearest neighbour (ENN).

NOTES

The Nearest Neighbour Index (ENN) analyse the Euclidean Nearest Neighbour to the first neighbouring patch. The output value is in pixel and can be converted to a distance values using g.region resolution information. r.pi.enn and r.pi.fnn provide the same analysis concerning the first nearest neighbour (NN), but are extended to the n-th NN. However due to code construction does the r.pi.index distance analysis to first ENN perform faster. Methods: The method operators determine what algorithm is applied on the patches. r.pi.index can perform the following operations:

Area
The Area computes the area of each patch.
Perimeter
The Perimeter computes the perimeter of each patch.
Area-Perimeter ratio
The Area-Perimeter ratio divides the patch perimeter by the area.
SHAPE Index
The SHAPE Index divides the patch perimete by the minimum perimeter possible for a maximally compact patch of the corresponding patch area.
Border Index
The Border Index ....
Compactness Index
The Compactness Index ....
Asymmetry Index
The Border Index ....
Fractal Dimension Index
The Fractal Dimension Index ....
Nearest Neighbour Index
The Nearest Neighbour Index computes the Euclidean distance to the first nearest neighbour patch.

EXAMPLE

Examples based on the North Carolina sample dataset are provided below. Indices are calculated for the landscape class 5 (forest). set region settings to used landcover class map:

g.region rast=landclass96

computation of patch size (patch definition: 4-neighbourhood rule)

r.pi.index input=landclass96 output=landclass96_forestclass5_area keyval=5 method=area
# improve colouring of resulting map:
r.colors landclass96_forestclass5_area col=bgyr

computation of patch size (patch definition: 8-neighbourhood rule)

r.pi.index input=landclass96 output=landclass96_forestclass5_area keyval=5 method=area -a

computation of patch isolation (euclidean distance to 1. nearest neighbour; patch definition: 4-neighbourhood rule)

r.pi.index input=landclass96 output=landclass96_forestclass5_ENN keyval=5 method=ENN -a

BUGS

Landscapes with more than 10 000 individual patches might cause a memory allocation error depending on the user's system.

AUTHORS

Programming: Elshad Shirinov
Scientific concept: Dr. Martin Wegmann
Department of Remote Sensing
Remote Sensing and Biodiversity Unit
University of Wuerzburg, Germany

Port to GRASS GIS 7: Markus Metz

SOURCE CODE

Available at: r.pi.index source code (history)
Latest change: Friday Feb 21 10:10:05 2025 in commit 7d78fe3