.TH d.correlate 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBd.correlate\fR\fR  - Prints a graph of the correlation between raster maps (in pairs).
.SH KEYWORDS
display, correlation, scatterplot
.SH SYNOPSIS
\fBd.correlate\fR
.br
\fBd.correlate help\fR
.br
\fBd.correlate\fR [\-\fBt\fR] \fBlayer1\fR=\fIstring\fR \fBlayer2\fR=\fIstring\fR  [\fBlayer3\fR=\fIstring\fR]   [\fBlayer4\fR=\fIstring\fR]   [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-t\fR" 4m
.br
Draw a trend line and calculate linear regression formula
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBlayer1\fR=\fIstring\fR" 4m
.br
raster input map
.IP "\fBlayer2\fR=\fIstring\fR" 4m
.br
raster input map
.IP "\fBlayer3\fR=\fIstring\fR" 4m
.br
raster input map
.IP "\fBlayer4\fR=\fIstring\fR" 4m
.br
raster input map
.PP
.SH DESCRIPTION
\fId.correlate\fR is a shell (sh(1)) script that
graphically displays the results of an
\fIr.stats\fR 
run on two raster map layers.  This shell script is useful
for highlighting the correlation (or lack of it) among data
layers (scattergram).
.PP
The results are displayed in the active display frame on
the user's graphics monitor.  \fId.correlate\fR erases
the active frame before displaying results.
.PP
The \fBlayer\fR\fIn\fR parameters supply the names of two to
four existing raster map layers to be included in the correlation.
.SH NOTES
This is a shell script that uses \fIr.stats\fR 
and the UNIX \fIawk\fR command to calculate the correlation among data
layers, and uses \fId.text\fR and 
\fId.graph\fR to display the results.
.PP
If three or four map layers are specified, the correlation
among each combination of two data layers is displayed.
.SH EXAMPLE
Compare LANDSAT-7 bands 2 and 3 in the North Carolina sample dataset,
and over-plot a trend line:
\fC
.DS
.br
  g.region rast=lsat7_2002_20
.br
  d.correlate \-t layer1=lsat7_2002_20 layer2=lsat7_2002_30 \-\-verbose
.br
.DE
\fR
.SH SEE ALSO
\fI
d.text,
d.graph,
r.coin,
r.regression.line,
r.stats
\fR
.SH AUTHORS
Michael Shapiro,
U.S.Army Construction Engineering 
Research Laboratory
.PP
Rewritten to GRASS 6 (from csh to sh) by Markus Neteler
.br
Linear regression model and trend line plotting by Hamish Bowman
.PP
\fILast changed: $Date: 2013-09-22 09:51:30 +0200 (Sun, 22 Sep 2013) $\fR
.PP
Full index
.PP
© 2003-2014 GRASS Development Team