r.li.patchdensity(1)

🦋 r.li.patchdensity (1) 🦋

hiii bestie, welcome to the GRASS GIS User's Manual page for r.li.patchdensity(1) — it's giving landscape-structure-analysis main character energy and honestly? we're obsessed. let's get into it 💖

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✨ NAME ✨

r.li.patchdensity — Calculates patch density index on a raster map, using a 4 neighbour algorithm

🏷️ KEYWORDS 🏷️

raster, landscape structure analysis, patch index

📜 SYNOPSIS 📜

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

🚩 Flags 🚩

• --overwrite — Allow output files to overwrite existing files (yes, it will simply replace what's there, no cap)
• --help — Print usage summary
• --verbose — Verbose module output (it will yap, affectionately)
• --quiet — Quiet module output (shhh era)
• --ui — Force launching GUI dialog

🧚 Parameters 🧚

• input=name [required] — Name of input raster map
• config=name [required] — Configuration file
• output=name [required] — Name for output raster map

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💖 DESCRIPTION 💖

r.li.patchdensity calculates the "patch density index", which is literally 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. so like, only the up/down/left/right besties count as neighbours, diagonals don't get a vote 🙈

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🌸 NOTES 🌸

Do not use absolute path names for the config and output file/map parameters. just don't, bestie, it's not the vibe.

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. no negatives here, we don't do that 💅

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🌈 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

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👀 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)

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💜 SOURCE CODE 💜

Available at: r.li.patchdensity source code (history)

Accessed: Saturday Jan 17 05:40:54 2026

Main index | Raster index | Topics index | Keywords index | Graphical index | Full index

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and that's the whole page, bestie — every flag, every path, every ≥ 0, all of it, fr fr. 🫶

this lil legend runs on GRASS 8.4.2, and the manual itself is the GRASS GIS 8.4.2 Reference Manual, © 2003-2025 GRASS Development Team. source + version + date all accounted for, periodt. ✨💅🎀