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<H1><A NAME="SECTION003020000000000000000"></A>
<A NAME="app:colorbars"></A><A NAME="32448"></A>
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M.2 Labeled and non-equidistant color legends
</H1>
The use of color legends has already been introduced in Chapter <A HREF="node120.html#ch:7">7</A> (examples 2, 16, and 17). Things become a bit more complicated when you want to label the legend with names for certain intervals (like geological time periods in the example below). To accomplish that, one should add a semi-colon and the label name at the end of a line in the cpt table and add the <B>-L</B> option to the <A NAME="tex2html1884"
HREF="../man/psscale.html"><I><B>psscale</B></I></A><A NAME="32484"></A> command that draws the color legend. This option also makes all intervals in the legend of equal length, even it the numerical values are not equally spaced.
<P>
Normally, the name labels are plotted at the lower end of the intervals. But by adding a <I>gap</I> amount (even when zero) to the <B>-L</B> option, they are centered. The example below also shows how to annotate ranges using <B>-Li</B> (in which case no name labels should appear in the cpt file), and how to switch the color bar around (by using a negative length).
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<PRE>#!/bin/sh
#
ps=GMT_App_M_2.ps
gmtset ANNOT_FONT_SIZE 10p MEASURE_UNIT cm
# Set up color palette with named annotations
cat > ages.cpt <<END
#COLOR_MODEL = RGB
#
0 197 0 255 23 197 0 255 ;Neogene
23 81 0 255 66 81 0 255 ;Paleogene
66 0 35 255 146 0 35 255 ;Cretaceous
146 0 151 255 200 0 151 255 ;Jurassic
200 0 255 244 251 0 255 244 ;Triassic
251 0 255 127 299 0 255 127 ;Permian
299 0 255 11 359 0 255 11 ;Carboniferous
359 104 255 0 416 104 255 0 ;Devonian
416 220 255 0 444 220 255 0 ;Silurian
444 255 174 0 488 255 174 0 ;Ordovician
488 255 58 0 542 255 58 0 ;Cambrian
B black
F white
END
# Top row, left to right. Using names.
psscale -Ef -Cages.cpt -D00/13/-8/0.5 -K > $ps
psscale -Ef -Cages.cpt -D04/13/-8/0.5 -O -K -L >> $ps
psscale -Ef -Cages.cpt -D08/13/-8/0.5 -O -K -L0.0 >> $ps
psscale -Ef -Cages.cpt -D12/13/-8/0.5 -O -K -L0.1 >> $ps
psscale -Ef -Cages.cpt -D16/13/+8/0.5 -O -K -L >> $ps
psscale -Ef -Cages.cpt -D20/13/+8/0.5 -O -K -L0.1 >> $ps
# Bottom row, left to right. Using numbers.
sed 's/;.*$//' ages.cpt > years.cpt
psscale -Ef -Cyears.cpt -D00/04/+8/0.5 -O -K >> $ps
psscale -Ef -Cyears.cpt -D04/04/-8/0.5 -O -K -L >> $ps
psscale -Ef -Cyears.cpt -D08/04/-8/0.5 -O -K -L0.0 >> $ps
psscale -Ef -Cyears.cpt -D12/04/-8/0.5 -O -K -L0.1 >> $ps
psscale -Ef -Cyears.cpt -D16/04/-8/0.5 -O -K -Li >> $ps
psscale -Ef -Cyears.cpt -D20/04/-8/0.5 -O -Li0.1 >> $ps
rm -f ages.cpt years.cpt
</PRE>
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<DIV ALIGN="CENTER"><A NAME="fig:GMT_App_M_2"></A><A NAME="32461"></A>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure M.2:</STRONG>
The many forms of color legends created by <A NAME="tex2html1881"
HREF="../man/psscale.html"><I><B>psscale</B></I></A><A NAME="32492"></A>.</CAPTION>
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<ADDRESS>
Paul Wessel
2010-01-14
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