r.regression.line(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

✨ r.regression.line ✨

okay bestie, welcome to r.regression.line 💖 this is the GRASS GIS User's Manual page for it, and we're about to make linear regression sound as cute as it actually is. (It's very cute. Trust.) 🎀

It does raster, statistics, and regression — those are the keywords, iykyk. 🌸

🌈 NAME 🌈

r.regression.line — calculates linear regression from two raster maps: y = a + b*x. literally the whole job 💅

🦋 SYNOPSIS 🦋

r.regression.line
r.regression.line --help
r.regression.line [-g] mapx=name mapy=name  [output=name]
[--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

🎀 Flags 🎀

  • -g — print it in shell script style, so it's all variable=value coded and ready to be eval'd. obsessed.
  • --overwrite — lets output files overwrite existing files. yes bestie, it will absolutely replace them, no cap.
  • --help — prints the usage summary. your bestie when you forget stuff 🫶
  • --verbose — verbose module output. the module gets chatty. we love that.
  • --quiet — quiet module output. the module shuts up. also valid.
  • --ui — forces launching the GUI dialog. clicky-clicky mode 🖱️

🌸 Parameters 🌸

  • mapx=name [required] — the map for the x coefficient. not optional, bestie, don't skip it.
  • mapy=name [required] — the map for the y coefficient. also required. also don't skip it.
  • output=name — an ASCII file for storing the regression coefficients. if you don't name a file, it just prints to the screen instead. main character behavior honestly.

💖 DESCRIPTION 💖

So. r.regression.line calculates a linear regression from two raster maps, according to this formula:

y = a + b*x

where x and y represent the input raster maps. that's it. that's the vibe. ✨

Optionally, it saves regression coefficients as an ASCII file. and the result includes all of these little icons:

  • offset/intercept (a)
  • gain/slope (b)
  • correlation coefficient (R)
  • number of elements (N)
  • means (medX, medY)
  • standard deviations (sdX, sdY)
  • and the F test for testing the significance of the regression model as a whole (F)

a whole little squad of statistics. 👑

📝 NOTES 📝

ngl the glow-up here is real: the results for offset/intercept (a) and gain/slope (b) are identical to what you get from R-stats's lm() function. same numbers, different font. 💅

🧚 EXAMPLE 🧚

Comparison of two DEMs (SRTM and NED, both at 30m resolution), provided in the North Carolina sample dataset:

g.region raster=elev_srtm_30m -p
r.regression.line mapx=elev_ned_30m mapy=elev_srtm_30m
 y = a + b*x
   a (Offset): -1.659279
   b (Gain): 1.043968
   R (sumXY - sumX*sumY/N): 0.894038
   N (Number of elements): 225000
   F (F-test significance): 896093.366283
   meanX (Mean of map1): 110.307571
   sdX (Standard deviation of map1): 20.311998
   meanY (Mean of map2): 113.498292
   sdY (Standard deviation of map2): 23.718307

Using the script style flag AND eval to make results available in the shell — this is the moment, bestie:

g.region raster=elev_srtm_30m -p
eval `r.regression.line -g mapx=elev_ned_30m mapy=elev_srtm_30m`
# print result stored in respective variables
echo $a
-1.659279
echo $b
1.043968
echo $R
0.894038

👀 SEE ALSO 👀

d.correlate, r.regression.multi, r.stats — go read those too, they're all in the same friend group 🫶

💜 AUTHORS 💜

  • Dr. Agustin Lobo - alobo at ija.csic.es
  • Updated to GRASS 5.7 Michael Barton, Arizona State University
  • Script style output Markus Neteler
  • Conversion to C module Markus Metz

🔥 SOURCE CODE 🔥

Available at: r.regression.line source code (history)

Accessed: Saturday Jan 17 05:40:57 2026

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

© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

and that's the whole page, bestie 💖 this was GRASS GIS 8.4.2, documented in that reference manual we just mentioned, and last accessed on Saturday Jan 17 05:40:57 2026 — go run a regression, you're gonna slay ✨👑💅

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