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Anders
Asked: 2015-05-24 07:42:58 +0800 CST

GNU Octave's legend function is broken

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I am having big troubles producing quality plots with the default GNU Octave (3.8.1) which comes with Ubuntu 14.04 LTS. I am trying to re-run some existing code (thousands of lines of code) and the code is broken because there are intermediate plots with legends here and there. I know that the code base is legitimate GNU Octave code.

Here is a minimal crashing example:

graphics_toolkit('gnuplot') # I need this for TeX-like labels,
                            # but I doubt this cause a trouble with legend
R = 2000; 
N = R/4;
t = (0:N-1)/R;
figure # plot without legend which works fine
plot(t*1000, sin(2*pi*100*t), 'b')
xlabel('t ms')
ylabel('p_e Pa')
figure # plot with legend which crash
plot(t*1000, sin(2*pi*100*t), 'b; sine wave;')
xlabel('t ms')
ylabel('p_e Pa')

This is the output in GNU Octave:

>> error: invalid value = northeast
>> error: set: invalid value for radio property "location" (value = northeast)
>> error: called from:
>> error:   /usr/share/octave/3.8.1/m/plot/appearance/legend.m at line 995, column 11
>> error:   /usr/share/octave/3.8.1/m/plot/draw/private/__plt__.m at line 149, column 7
>> error:   /usr/share/octave/3.8.1/m/plot/draw/plot.m at line 220, column 10
octave

2 Answers

  1. Steeldriver, you saved my weekend. Thanks a lot! I had the same problem as the bug in

    http://savannah.gnu.org/bugs/?41390

    and it was sufficient to remove the package

    sudo apt remove octave-strings

    from the Ubuntu package repository. It seems like the default GNU Octave package is not compatible with all of the Octave-Forge "add-on" packages in the default repository. Are you able to reproduce the bug by installing that package? Maybe this inconsistency should be reported somewhere.

    Btw, the output of 

    apt-cache policy octave-strings

    was

    >> octave-strings:
>> Installé : 1.1.0-1build1
>> Candidat : 1.1.0-1build1 
>> Table de version :
>> *** 1.1.0-1build1 0
>>     500 http://fr.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
>>     100 /var/lib/dpkg/status

    and the output of

    apt-cache policy octave

    is

    >> octave:
>> Installé : 3.8.1-1ubuntu1
>> Candidat : 3.8.1-1ubuntu1
>> Table de version :
>> *** 3.8.1-1ubuntu1 0
>>    500 http://fr.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
>>    100 /var/lib/dpkg/status
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  2. Best Answer

    I had the same problem and when removing octave-strings caused other errors. So instead, I've used the "try" statement, as follows:

    try
  legend(["str1 "; "str2"; "str3"; "str4"; "str5"], 
          "location", "northeast",
          "orientation", "vertical");
catch
end_try_catch

    This seems to do the trick.

    • 0