bugGNU Octave - Bugs: bug #42881, Error Plotting Function in Octave


bug #42881: Error Plotting Function in Octave

Submitted by:  Brandon Morrison <bmorrison>
Submitted on:  Wed 30 Jul 2014 11:15:49 PM UTC  
Category:  Plotting Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Need Info Assigned to:  None
Originator Name:  bmorrison Open/Closed:  Closed
Release:  3.8.1 Operating System:  GNU/Linux

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Mon 11 Aug 2014 05:58:58 PM UTC, comment #4:

No response to request for info. Assume problem is solved and closing report.

Rik <rik5>
Project Administrator
Thu 31 Jul 2014 01:13:40 PM UTC, comment #3:

Ok, I think I understand what you are seeing. If you type 'q' in the Octave command window does the plot respond as you expect?

If so, then here is what is happening:

Octave uses a screen pager by default to show the output of commands one screen at a time. In your script, if the x vector is too large, it will trigger the pager which is waiting for you to command it to scroll or to exit. This prevents the plot from responding because your command has not returned control to the Octave prompt yet.

If you want to disable the pager to let the data scroll to the command window no matter how large it is, type "more off" or "page_screen_output (false)" at the Octave prompt. This can be added to your octaverc startup file to make this a permanent preference.

Mike Miller <mtmiller>
Project Administrator
Thu 31 Jul 2014 04:58:07 AM UTC, comment #2:

I was using Octave 3.8.1 in the built-in gui interface (entering octave--force-gui at the command prompt in linux). I was using the built-in editor, saved the file, and with a step value of 1, nothing but a grey graph window was shown. For other values, it worked beautifully.

We copied this exact code into MATLAB, which was installed on an Apple Macbook Pro, and the code performed beautifully for all values, including 1.

I am not 100% sure what plotting software I am using, as I installed the software directly from the Science Repository for OpenSUSE. I looked information about Octave on its openSUSE page and believe that it is making use of graphics_toolkit.

Brandon Morrison <bmorrison>
Thu 31 Jul 2014 03:49:33 AM UTC, comment #1:

Thanks for your bug report. I don't see any problem with the attached script in Octave 3.8.1 here. Can you describe how you are running the script (at the Octave interpreter prompt, from the system shell, or within Emacs or QtOctave?) or what variations you have tried that have either worked or not worked? Which plotting engine are you using (graphics_toolkit)?

Mike Miller <mtmiller>
Project Administrator
Wed 30 Jul 2014 11:15:49 PM UTC, original submission:

The code (see attached octave file) is supposed to be a simple array. The array is defined for x. The step value of 1 will NOT plot, it will freeze instead. For any other step value, the graph will plot.

We further tested the code on an Apple system using MATLAB. For all values of the step value, it graphs. Thus, there is a discrepancy between Octave 3.8.1 and MATLAB

Brandon Morrison <bmorrison>


(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:

Attached Files
file #31802:  Graph2.m added by bmorrison (93B - text/x-matlab)


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2014-08-11 rik5 Open/ClosedOpen => Closed
    2014-07-31 mtmiller StatusNone => Need Info
    2014-07-30 bmorrison Attached File- => Added Graph2.m, #31802

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