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<title>ploticus: legend-driven technique</title>
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  <td><br><h2>Legend-driven technique</h2></td>
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.TH Legend-driven_technique PL "10-DEC-2001   PL ploticus.sourceforge.net"

.LP
"Legend-driven technique" allows 
bar color, scatterplot symbol, etc. to be controlled by a data field.
This technique involves defining a legend \fIfirst\fR, containing information
to associate data field contents with appearance details.
Then the plotting is done.

.LP
Here is the procedure:
.IP
1. For every expected variation (bar color, scatterplot symbol, or whatever) 
set up an explicit legend entry using 
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\0proc legendentry
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\0.  Label, tag, and details attributes should be supplied.
The tag will be compared with data field contents.
The details attributes control appearance.
.IP
2. Plot, using the appropriate attribute.  For example, if you are
doing a bar graph where individual bar colors are controlled by a data
field, you would use \fBproc bars\fR and specify a \fCcolorfield\fR.


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