#646 Parallel axis plots

[Ethan Merritt]

This patch implements a parallel coordinate axis plotting style.
This is a longstanding requested feature that is relatively rare in plotting programs.
See:
https://sourceforge.net/p/gnuplot/feature-requests/142/
http://en.wikipedia.org/wiki/Parallel_coordinates

Here is sample output:
http://gnuplot.sourceforge.net/demo_cvs/parallel.html

Here is the documentation section:

gnuplot> help parallelaxes

Parallel axis plots offer a way of presenting correlation in a multidimensional
data set. Each input column is associated with a separately scaled vertical
axis. The column values read from each line of input are connected by line
segments drawn from axis 1 to axis 2 to axis 3 and so on. That is, each line
of input is represented by a separate line in the parallel axes plot.
It is common use some discrete categorization to assign line colors, allowing
visual exploration of the corellation between this categorization and the axis
dimensions.
By default gnuplot will automatically determine the range and scale of the
individual axes from the input data, but the usual axis range and scale
commands can be used to override this. See set prange and set ptics.

The basic command is
plot 'data' using 1:2:3:4:5:6 with parallelaxes

You must give at least three columns, but you can give many more if you like.

Please test and comment on syntax, etc.

[Ethan Merritt]

• Description has changed:

Diff:

--- old
+++ new
@@ -23,3 +23,11 @@
  individual axes from the input data, but the usual axis range and scale
  commands can be used to override this.  See `set prange` and `set ptics`.

+The basic command is

+  plot 'data' using 1:2:3:4:5:6  with parallelaxes
+
+You must give at least three columns, but you can give many more if you like.
+
+
+Please test and comment on syntax, etc.  
+

• Group: -->

[Ethan Merritt]

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