[Pkg-octave-devel] Bug#783624: Bad plotted data against time with long arrays

[Rafael Laboissiere <rafael@laboissiere.net>]

Control: tags -1 = upstream confirmed

* Marco Bajo <marco.bajo@gmail.com> [2015-04-29 15:49]:

> The bug arises using Octave 3.8.2, when plotting an array of data 
> against an array of times. Times is an array created with datenum with 
> a step of 10 minutes between records. The trend of plotted data is made 
> by segments and it is not continuous as it should be. Plotting data 
> alone, not against time, or using Octave 3.6.2 gives a correct curve. I 
> attach the m-file and the dataset need to reproduce the bug.

I can obtain non-jagged curves from your data using either this:

    close all
    graphics_toolkit ("gnuplot")
    plot (ttr, currr)

or this:

    close all
    graphics_toolkit ("fltk")
    plot (ttr - floor (ttr (1)), currr)

Notice that fltk is the default graphics toolkit.  This is the reason you 
do not see what you expect when you run:

    plot (ttr, currr)

without changing the graphics toolkit from the default.

At any rate, this is an upstream issue and I am hereby tagging this bug 
report accordingly.  It is related to the specific numerical condition of 
your data.  This is the reason why the problem disappears when 
floor(ttr(1)) is subtracted from ttr.

I will report this upstream, eventually.

Thanks,

Rafael