1r.regression.line(1) GRASS GIS User's Manual r.regression.line(1)
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6 r.regression.line - Calculates linear regression from two raster maps:
7 y = a + b*x.
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10 raster, statistics, regression
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13 r.regression.line
14 r.regression.line --help
15 r.regression.line [-g] mapx=name mapy=name [output=name] [--over‐
16 write] [--help] [--verbose] [--quiet] [--ui]
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18 Flags:
19 -g
20 Print in shell script style
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22 --overwrite
23 Allow output files to overwrite existing files
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25 --help
26 Print usage summary
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28 --verbose
29 Verbose module output
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31 --quiet
32 Quiet module output
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34 --ui
35 Force launching GUI dialog
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37 Parameters:
38 mapx=name [required]
39 Map for x coefficient
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41 mapy=name [required]
42 Map for y coefficient
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44 output=name
45 ASCII file for storing regression coefficients (output to screen if
46 file not specified).
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49 r.regression.line calculates a linear regression from two raster maps,
50 according to the formula
51 y = a + b*x
52 where
53 x
54 y
55 represent the input raster maps.
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57 Optionally, it saves regression coefficients as a ASCII file. The re‐
58 sult includes the following coefficients: offset/intercept (a) and
59 gain/slope (b), correlation coefficient (R), number of elements (N),
60 means (medX, medY), standard deviations (sdX, sdY), and the F test for
61 testing the significance of the regression model as a whole (F).
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64 The results for offset/intercept (a) and gain/slope (b) are identical
65 to that obtained from R-stats’s lm() function.
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68 Comparison of two DEMs (SRTM and NED, both at 30m resolution), provided
69 in the North Carolina sample dataset:
70 g.region raster=elev_srtm_30m -p
71 r.regression.line mapx=elev_ned_30m mapy=elev_srtm_30m
72 y = a + b*x
73 a (Offset): -1.659279
74 b (Gain): 1.043968
75 R (sumXY - sumX*sumY/N): 0.894038
76 N (Number of elements): 225000
77 F (F-test significance): 896093.366283
78 meanX (Mean of map1): 110.307571
79 sdX (Standard deviation of map1): 20.311998
80 meanY (Mean of map2): 113.498292
81 sdY (Standard deviation of map2): 23.718307
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83 Using the script style flag AND eval to make results available in the
84 shell:
85 g.region raster=elev_srtm_30m -p
86 eval `r.regression.line -g mapx=elev_ned_30m mapy=elev_srtm_30m`
87 # print result stored in respective variables
88 echo $a
89 -1.659279
90 echo $b
91 1.043968
92 echo $R
93 0.894038
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96 d.correlate, r.regression.multi, r.stats
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99 Dr. Agustin Lobo - alobo at ija.csic.es
100 Updated to GRASS 5.7 Michael Barton, Arizona State University
101 Script style output Markus Neteler
102 Conversion to C module Markus Metz
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105 Available at: r.regression.line source code (history)
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107 Accessed: Saturday Jan 21 21:15:05 2023
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109 Main index | Raster index | Topics index | Keywords index | Graphical
110 index | Full index
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112 © 2003-2023 GRASS Development Team, GRASS GIS 8.2.1 Reference Manual
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116GRASS 8.2.1 r.regression.line(1)