[Octave-bug-tracker] [bug #53832] Fractional independent variable mis-plotting in Qt, not Gnuplot.

[AlanRobertClark]

URL:
  <http://savannah.gnu.org/bugs/?53832>

                 Summary: Fractional independent variable mis-plotting in Qt,
not Gnuplot.
                 Project: GNU Octave
            Submitted by: alanrobertclark
            Submitted on: Fri 04 May 2018 11:01:53 AM UTC
                Category: Plotting
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: AlanRobertClark
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.2.2
        Operating System: GNU/Linux

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Details:

Independant data is a timestamp, dependant data is Blood Glucose.

I have attempted to include the files to demonstrate the offset diamond
markers on the plot. Under certain circumstances, the error is quite large,
and I have confirmed the error under 4.4 (flatpak version)

plotbug.m: 

% Shows Qt vs gnuplot for fractional x data (datenum)
load bg.dat
figure('MenuBar','none');
plot(bg(:,1),bg(:,2),'-d');
grid on;

graphics_toolkit('gnuplot');
figure('MenuBar','none');
plot(bg(:,1),bg(:,2),'-d');
grid on;


The error was noted as I overplot ``points-of-interest'' using a plain marker
over a line plot, and I noted that the marker was not at the vertex. Caused
serious hair-loss. 



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File Attachments:


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Date: Fri 04 May 2018 11:01:54 AM UTC  Name: plotbug.m  Size: 222B   By:
alanrobertclark

<http://savannah.gnu.org/bugs/download.php?file_id=44084>
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Date: Fri 04 May 2018 11:01:54 AM UTC  Name: qt.png  Size: 16KiB   By:
alanrobertclark

<http://savannah.gnu.org/bugs/download.php?file_id=44085>
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Date: Fri 04 May 2018 11:01:54 AM UTC  Name: bg.dat  Size: 408B   By:
alanrobertclark

<http://savannah.gnu.org/bugs/download.php?file_id=44086>
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Date: Fri 04 May 2018 11:01:54 AM UTC  Name: gnuplot.png  Size: 15KiB   By:
alanrobertclark

<http://savannah.gnu.org/bugs/download.php?file_id=44087>

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