[Octave-bug-tracker] [bug #43559] "hold on" causes "plot" to use incorrect series colouring

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?43559>

                 Summary: "hold on" causes "plot" to use incorrect series
colouring
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Fri 07 Nov 2014 12:11:20 UTC
                Category: Plotting
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: A. Tombs
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.2
        Operating System: GNU/Linux

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Details:

Each invocation of "plot" should use the same colour order for data series
(usually Blue Green Red etc.). The "hold on" command should cause the graphs
produced by each "plot" command to be drawn on the same figure.

It seems to me that when a "hold on" is issued, the colour orders used for the
subsequent "plot" calls are modified in a non-trivial way.

To reproduce, run the following:


x=[0;1];
y=[0,0,0;1,2,3];
figure;
plot(x,y);
hold on;
z = y+[0,0,0;0.5,0.5,0.5];
plot(x,z);


Expected: Six lines plotted with colours (in ascending order) Blue, Blue,
Green, Green, Red, Red.

Observed: Six lines plotted with colours Blue, Blue, Green, Magenta, Red, Dark
Yellow.

It seems as though "hold on" causes the first series of the second plot to use
the correct colour (Blue), but the other series use incorrect colours from
further along in the colour order.

This behaviour conflicts with Matlab and previous versions of Octave (I tested
3.6.0, which shows the expected behaviour).

Note that his behaviour is also different from the "hold all" command, which
causes the subsequent "plot" calls to continue through the default colour
order. "hold all" seems to be implemented correctly, giving Blue, Cyan, Green,
Magenta, Red, Dark Yellow in my above example.




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