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From: sfeam <sfeam@users.sourceforge.net>
Newsgroups: comp.graphics.apps.gnuplot
Subject: Re: splot with variably translucent points
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Date: Thu, 22 Sep 2011 19:05:09 -0700
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fearless_fool wrote:

> I want to visualize a minimization problem over three input variables
> and one result.  With only two input variables, the visualization
> problem would be trivial.

Isn't this just a 3D heat map?
E.g. 3rd plot in 
    http://gnuplot.sourceforge.net/demo_cvs/heatmaps.html
 
> My thought is to use splot to plot 3D points, with the most opaque
> point(s) representing the minima, and more translucent points as it
> deviates from the minima.  This way, you should be able to see a
> cluster of dark points near the minimum.
> 
> How do I set the transparency of each point from the input data?

Sorry, the only plot style that currently supports variable alpha
is "with rgbalpha".
 
> Without variable transparency, I've got something as follows.  I'd
> like to use $4 to control the transparency.
> ===========
> set terminal pngcairo truecolor
> set view 60, 136, 1.22, 1.26
> splot "-" using 1:2:3 with points pointtype 7 pointsize 2 linecolor
> rgb '#444444'
> 3 -4 -4 37.767
> 3 -4 -6 37.744
> ...
> end
> 
> ===========