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r.regression.line(1grass) | Grass User's Manual | r.regression.line(1grass) |
NAME¶
r.regression.line - Calculates linear regression from two raster maps: y = a + b*x.KEYWORDS¶
raster, statistics, regressionSYNOPSIS¶
r.regression.liner.regression.line --help
r.regression.line [-g] mapx=name mapy=name [output=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:¶
- -g
-
Print in shell script style - --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:¶
- mapx=name [required]
-
Map for x coefficient - mapy=name [required]
-
Map for y coefficient - output=name
-
ASCII file for storing regression coefficients (output to screen if file not specified).
DESCRIPTION¶
r.regression.line calculates a linear regression from two raster maps, according to the formulay = a + b*xwhere
x yrepresent the input raster maps.
Optionally, it saves regression coefficients as a ASCII file. The result includes the following coefficients: offset/intercept (a) and 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).
NOTES¶
The results for offset/intercept (a) and gain/slope (b) are identical to that obtained from R-stats’s lm() function.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:
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.statsAUTHORS¶
Dr. Agustin Lobo - alobo at ija.csic.esUpdated to GRASS 5.7 Michael Barton, Arizona State University
Script style output Markus Neteler
Conversion to C module Markus Metz
Last changed: $Date: 2015-10-27 18:40:48 +0100 (Tue, 27 Oct 2015) $
SOURCE CODE¶
Available at: r.regression.line source code (history)Main index | Raster index | Topics index | Keywords index | Graphical index | Full index
© 2003-2016 GRASS Development Team, GRASS GIS 7.2.0 Reference Manual
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