GRASS GIS manual: d.correlate

Note: This document is for an older version of GRASS GIS that is outdated. You should upgrade, and read the current manual page.

NAME

d.correlate - Prints a graph of the correlation between raster maps (in pairs).

KEYWORDS

display, correlation, scatterplot

SYNOPSIS

d.correlate
d.correlate help
d.correlate [-t] layer1=string layer2=string [layer3=string] [layer4=string] [--verbose] [--quiet]

Flags:

-t: Draw a trend line and calculate linear regression formula
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

layer1=string: raster input map
layer2=string: raster input map
layer3=string: raster input map
layer4=string: raster input map

DESCRIPTION

d.correlate is a shell (sh(1)) script that graphically displays the results of an r.stats run on two raster map layers. This shell script is useful for highlighting the correlation (or lack of it) among data layers (scattergram).

The results are displayed in the active display frame on the user's graphics monitor. d.correlate erases the active frame before displaying results.

The layern parameters supply the names of two to four existing raster map layers to be included in the correlation.

NOTES

This is a shell script that uses r.stats and the UNIX awk command to calculate the correlation among data layers, and uses d.text and d.graph to display the results.

If three or four map layers are specified, the correlation among each combination of two data layers is displayed.

EXAMPLE

Compare LANDSAT-7 bands 2 and 3 in the North Carolina sample dataset, and over-plot a trend line:

  g.region rast=lsat7_2002_20
  d.correlate -t layer1=lsat7_2002_20 layer2=lsat7_2002_30 --verbose

AUTHORS

Michael Shapiro, U.S.Army Construction Engineering Research Laboratory

Rewritten to GRASS 6 (from csh to sh) by Markus Neteler
Linear regression model and trend line plotting by Hamish Bowman

Last changed: $Date: 2013-09-21 04:22:54 -0700 (Sat, 21 Sep 2013) $

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