matlab's addpoints function stopped working, it says that I'm trying to use the script as a function

Hello,

I'm just trying to add points to an animated line like this:

    f=figure('Visible','on','units','normalized','outerposition',[0 0 1 1],'Numbertitle','off','Name','test');
    for i=1:2
    	S(i)=subplot(2,1,i,'Parent',f);
    	h(i)=animatedline(S(i),'color','b','marker','.');
    end
    i=1;x=[1 2];
    for j=1:numel(h)
    	addpoints(h(j),i,x(j));
    end

But I get this error:

    Attempt to execute SCRIPT addpoints as a function:
    /usr/local/MATLAB/R2019b/toolbox/matlab/graphics/addpoints.m

Note that last time I used it it worked just fine...

BTW, I'm using matlab r2019b under ubuntu 18.04.

I went to matlab's install directory and `find . -type f -name "addpoints.m"` give me this:

    ./mcr/toolbox/matlab/graphics/addpoints.m
    ./toolbox/distcomp/array/+parallel/+internal/+array/@PlottableUsingGather/addpoints.m
    ./toolbox/matlab/graphics/addpoints.m

Of those 3, only the last one isn't empty and it just a help file, no function there...

[Adam Danz]

From Matlab's command window, determine if the addpoints function is being shadowed.

which addpoints -all
% The result for me:
% C:\Program Files\MATLAB\R2019b\toolbox\matlab\graphics\addpoints.m

[kira]

/usr/local/MATLAB/R2019b/toolbox/matlab/graphics/addpoints.m

addpoints is a built-in method                                % matlab.graphics.animation.AnimatedLine method

[Adam Danz]

I don't know what the distcomp toolbox is on your system and I don't have the time now to research what that might be. But my guess is that the addpoints file within that toolbox is a script and at some point it's overshadowing the builtin function.

Next time the error occurs you could test this by adding the path to the built-in function which should solve the problem.

[kira]

i added

addpath('/usr/local/MATLAB/R2019b/toolbox/matlab/graphics/');

to my script but the problem persist...

[Steven Lord]

Adam Danz: toolbox/distcomp contains files for Parallel Computing Toolbox. That toolbox was originally called Distributed Computing Toolbox but it was renamed several years ago. So that's okay.

In addition, it is in a folder whose name starts with the @ symbol. That makes that folder a MATLAB class folder and makes that file a method of that class. Classes defined in classdef files aren't required to be in a directory whose name starts with the @ symbol (unless they want to implement one or more methods in a separate file rather than inside the classdef file) but they are allowed to be. Older classes are required to be in a directory whose name starts with the @ symbol. So

    ./toolbox/distcomp/array/+parallel/+internal/+array/@PlottableUsingGather/addpoints.m

is the addpoints method for the parallel.internal.array.PlottableUsingGather class that is part of Parallel Computing Toolbox. [Since it is in an internal package, we don't recommend you use it directly.] It's only going to be called if one of the inputs is a parallel.internal.array.PlottableUsingGather object. But that might be a problem for a different reason than you think. I'll elaborate in an answer.

[Adam Danz]

Thanks for the explanation, Steven!

Answer 1

[Steven Lord]

What is the MATLAB root directory for your installation? You can find this using the command:

matlabroot

Are you certain that your current directory is not under matlabroot for a different installation of MATLAB, perhaps an older one?

I have Parallel Computing Toolbox installed in release R2019b (albeit on Windows) and I do not have a distcomp subdirectory under matlabroot\toolbox. According to the Release Notes for release R2019b the folder containing Parallel Computing Toolbox functionality was renamed so you shouldn't have toolbox/distcomp unless you added an older version of that directory to your MATLAB path or copied it over from an older installation (which will not work.)

So I'm wondering if your MATLAB path and/or your installation are in a bad state. To try to reset the MATLAB path back to its factory-installed state you could use the restoredefaultpath function. If you copied files or directories into your installation cleaning up the problem may be more involved.

[kira]

I do have two matlab installations, and what I posted originaly was indeed from the 2018b directory.

Now, in the 2019b (/usr/local/MATLAB/R2019b) directory I got the following from find . -type f -name "addpoints.m":

./mcr/toolbox/parallel/array/+parallel/+internal/+array/@PlottableUsingGather/addpoints.m
./mcr/toolbox/matlab/graphics/addpoints.m
./toolbox/parallel/array/+parallel/+internal/+array/@PlottableUsingGather/addpoints.m
./toolbox/matlab/graphics/addpoints.m

First 2 are empty, latest 2 are help files...

I did the restore path and the problem is still present...