r.pi.fnn - GRASS GIS manual

Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

NAME

r.pi.fnn - Determines patches of given value and performs a nearest-neighbor analysis.

KEYWORDS

raster

SYNOPSIS

r.pi.fnn

r.pi.fnn --help

r.pi.fnn [-a] input=name costmap=string output=name keyval=integer method=string[,string,...] number=num[-num][,num[-num],...] statmethod=string [dmout=string] [adj_matrix=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]: Name of input raster map
costmap=string [required]: Name of existing raster file with path-cost information
output=name [required]: Name for output raster map
keyval=integer [required]: Key value
method=string[,string,...] [required]: Operation to perform on fragments; Options: distance, path_distance, area, perimeter, shapeindex
number=num[-num][,num[-num],...] [required]: Number of nearest neighbors to analyse
statmethod=string [required]: Statistical method to perform on the values; Options: average, variance, standard deviation, value, sum
dmout=string: Output name for distance matrix and id-map (performed if not empty)
adj_matrix=string: Output name for adjacency matrix (performed if not empty)
title="phrase": Title for resultant raster map

DESCRIPTION
NOTES
EXAMPLE
SEE ALSO
AUTHORS

DESCRIPTION

Determine the functional nearest-neighbor distance analysis. r.pi.fnn is a patch based ecological/functional nearest neighbour analysis module. It computes distance based on a friction map. This module is related to r.pi.enn but more adequate if the ecological connectivity should be analysed.

NOTES

The calculation of the ecolgogical nearest neighbour is based on a raster with start patches. The actual map can be categorical or continuous but the value defined in keyval will be the basis for the patches to calculate the methods defined below. These patches will also be in the output map. The calculation of the ecolgogical nearest neighbour is based on a costmap (* and 1-infinite) - this map can be binary or continous - high values are considered to have high cost issues and the shortest path is the one with the lowest amount of costs. "null" values can not be traversed, hence these values have to be bypassed. "0" values are not accepted and will result in "0" distance.

e.g. if a binary map(1 and 2) is used, the the path with the lowest amount of "1" is chosen The number is the amount of nearest neighbours to be taken and the calculated distances are processed as assigned in statmethod Operations which r.pi.fnn can perform are:

Distance: The Distance to Nearest computes the nearest edge-to-edge distance between patches. Counting from the focus patch.
path Distance: The Distance to Nearest computes the nearest edge-to-edge distance between patches. Unlike Distance the distance is computed based on subsequent NN not from the focus patch onwards. The 1th NN is the first patch with the minimal edge-to-edge distance from the focus patch, while 2th NN is the patch with the minimal edge-to-edge distance from the 1th NN patch and so on.
Area: The Area computes the size of the nearest edge-to-edge distance patch. It is based on Distance not on path Distance.
Perimeter: The Perimeter computes the Perimeter of the nearest edge-to-edge distance patch. It is based on Distance not on path Distance.
SHAPE: The SHAPE computes the SHAPE Index of the nearest edge-to-edge distance patch. It is based on Distance not on path Distance.

The statsmethod operators determine calculation is done on the distance. Average, Variance,Stddev and value can be used.

Average: The Average computes the average value defined in Operations to perform .
Variance: The Variance computes the variance defined in Operations to perform .
Stand. Dev.: The Stand. Dev. computes the stddev value defined in Operations to perform .
Value: The patch Distance computes the nearest edge-to-edge distance between two patches. The output of value is the actual value. E.g. NN==5 of area gives the size of the 5th NN while Average gives the average of the area of 1-5th NN.

The input options are either one NN: 1 or several NN separated by ,: 1,2,5,8 or a range of NN: 1-6.

Merging these options is possible as well: 1-5,8,9,13,15-19,22 etc.

EXAMPLE

An example for the North Carolina sample dataset: Computing the functional or ecological distance to the first to nth nearest neighrbours using a cost matrix:

r.mapcalc "cost_raster = if(landclass96==5,1,if(landclass96 == 1, 10, if (landclass96==3,2, if(landclass96==4,1,if(landclass96==6,100)))))"
r.pi.fnn input=landclass96 keyval=5 costmap=cost_raster output=fnn1 method=distance number=10 statmethod=average

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.fnn source code (history)

Latest change: Monday Jun 28 07:54:09 2021 in commit: 1cfc0af029a35a5d6c7dae5ca7204d0eb85dbc55