## NAME

**r.pi.index** - Basic patch based indices

## KEYWORDS

raster
## SYNOPSIS

**r.pi.index**

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

### Flags:

**-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
**--ui**
- Force launching GUI dialog

### Parameters:

**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
- Options:
*area, perimeter, shape, border, compactness, asymmetry, area-perimeter, fractal, ENN*
**title**=*"phrase"*
- Title for resultant raster map

*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).

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.

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

*
r.pi.enn,
r.pi.import,
r.pi.rectangle,
r.pi
*
Landscapes with more than 10 000 individual patches might cause a memory
allocation error depending on the user's system.

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: Wed Feb 2 21:46:15 2022 in commit: 2e3dcb5eafe36d640aa68585be0192f07ca1eabb

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GRASS Development Team,
GRASS GIS 8.0.3dev Reference Manual