## DESCRIPTION

r.li.cwed (contrast weighted edge density) calculates the edge density between patch types specified:

with:

- k: attribute
- m: number of non-null attributes in the sampling area
- eik: total length of edge in landscape between patch types i and k
- dik: dissimilarity (edge contrast weight) between patch types i and k
- Area: total landscape area

The input file contains a row for each couple of patch type that we want to consider in the calculation. Each row must be saved using this syntax:
patchType1,patchType2,dissimilarityBetweenPatchType1andPatchType2

## 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\GRASS7\r.li\output\` (MS-Windows) or `$HOME/.grass7/r.li/output/` (GNU/Linux).

If the sample area contains only NULL values it is considered to have 0 patch and CWED=0. If Area is 0 r.li.cwed returns -1. This is only possible if the map is masked.
If you want to change these -1 values to NULL, run subsequently on the resulting map:

    r.null setnull=-1 input=my_map

after index calculation.

## EXAMPLES

To calculate the contrast weighted edge 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.cwed input=my_map conf=my_conf output=my_out \
              path=/path/to/weights.csv

Example for input "weights.csv" file:

    12,16,0.65
    44,123,0.32
    56,12,0.54
    23,66,0.99

## 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

Serena Pallecchi student of Computer Science University of Pisa (Italy).
Commission from Faunalia Pontedera (PI), Italy (www.faunalia.it)
Markus Metz