bugGNU Octave - Bugs: bug #43782, single precision is insufficient...

 
 

bug #43782: single precision is insufficient for plotting

Submitted by:  None
Submitted on:  Mon 08 Dec 2014 08:58:47 PM UTC  
 
Category: Plotting with OpenGLSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Inaccurate Result
Status: DuplicateAssigned to: None
Originator Name: Chad AeschlimanOriginator Email: -unavailable-
Open/Closed: ClosedRelease: 3.8.2
Operating System: Any

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Tue 09 Dec 2014 09:24:39 AM UTC, comment #2:

The rescaling has been proposed for quite a long
time. Any volunteers??

Michael Godfrey <godfrey>
Project Member
Mon 08 Dec 2014 09:35:54 PM UTC, comment #1:

Duplicate of bug #33748, which itself is a duplicate of a much earlier bug report.

Yes this can be annoying.
I hit this when plotting time series with datenums on the X-axis in a range within recent decades, say [712224:734139] (years 1950 - 2010), indeed much lower than 10^38, rather 10^6, for an example see the other bug report.

I've once peeked at the innards of the plotting system but that stuff is way beyond me. The wait is for someone proficient in OpenGL who wants to tackle this.

Both graphics_toolkit fltk and qt are affected.

Philip Nienhuis <philipnienhuis>
Project Member
Mon 08 Dec 2014 08:58:47 PM UTC, original submission:

The new plotting system apparently uses single precision for plotting (https://www.gnu.org/software/octave/doc/interpreter/Introduction-to-Plotting.html). This is not sufficient for scientific applications. The website claims that it is a factor when plotting large values (10^38) but really it becomes a precision problem at much smaller values. For example, The following two figures should look the same, just the x axis is shifted in the second:

Anonymous

 

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Attached Files
file #32622:  fig1.png added by None (22KiB - image/png)
file #32623:  fig2.png added by None (12KiB - image/png)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -unavailable- added by godfrey (Posted a comment)
  • -unavailable- added by None (Submitted the item)
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    Follow 5 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Mon 08 Dec 2014 09:35:54 PM UTCphilipnienhuisStatusNone=>Duplicate
      Open/ClosedOpen=>Closed
      Operating SystemGNU/Linux=>Any
    Mon 08 Dec 2014 08:58:47 PM UTCNoneAttached File-=>Added fig1.png, #32622
      Attached File-=>Added fig2.png, #32623

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