Update gramm plot matlab crashing - matlab

Question

I have a MATLAB GUI that calls an external function to make a plot (make_ethogram_plot).
The idea would be to have an external figure that is constantly updated with the output value from the figure. Every time the data gets updated it should replot the values, it updates at ~10 Hz. I chose gramm (https://github.com/piermorel/gramm/tree/master/%40gramm) because it is really easy to make a raster plot.
This is the function that gets called. I am having issues to
1) Make it only update in the parent figure with specific name, instead of plotting in the GUI(which is the active figure).
2) Make it not crash. It would open many figures or open or close the same figure at 10 Hz until crashing.
In this configuration, it gives error because it doesn't find g after the first plot. Making g , f, and p1 globals makes it crash (opens every time it gets called)
function make_ethogram_plot(datastructure)
% if the figure doesn't exists create it
if(isempty(findobj(0, 'Name', 'My_gramm_ethogram')))
f=figure('Name', 'My_gramm_ethogram');
p1 = uipanel('Parent',f,'BackgroundColor',[1 1 1],'BorderType','none');
g = gramm('x', datastructure.final_data.frameID, 'color', categorical(datastructure.final_data.behavior));
g.geom_raster();
g.set_parent(p1);
g.draw()
else
% defining f,p1, g here (or having them global) works but crashes
% due to refresh rate
g.update()
end
end

Answer 1

I wrote this code to try to replicate your problem:
function animate_random_data
N = 10000;
data = [cumsum(rand(N,1)),randn(N,1)];
for ii=0:1000
% Plot the data
make_ethogram_plot(data);
drawnow
% Compute new data
data(:,1) = cumsum(rand(N,1));
data(:,2) = randn(N,1);
end
function make_ethogram_plot(data)
fig = findobj(0, 'Name', 'My_gramm_ethogram');
if(isempty(fig))
% If the figure doesn't exists create it
fig = figure('Name', 'My_gramm_ethogram');
ax = axes(fig);
plot(ax,data(:,1),data(:,2));
drawnow
set(ax,'xlimmode','manual','ylimmode','manual');
else
% If it does, update it
line = findobj(fig,'type','line');
set(line,'xdata',data(:,1));
set(line,'ydata',data(:,2));
end
Here, I followed your concept of looking for a named figure window, and creating one if it didn't exist. However, if it does exist, I simply replace the XData and YData property of the line that is already there. This is the fastest way of animating a graph, much faster than deleting the existing plot and creating a new one. After plotting, I use drawnow to update the display. I set XLimMode and YLimMode to manual to prevent re-computation of axes limits and consequent re-drawing of the axes.
The function took 17 seconds to draw all 1000 frames, meaning it's drawing about 60 frames a second. It does not (and should not) crash MATLAB.
You can limit the display rate to 20 frames/sec with drawnow limitrate. It will skip updating the display if the frames come too fast.
I don't know what the gramm/update method does, the class is too complicated to quickly see what is going on, but I dare presume it deletes the axes and creates a new plot from scratch. Not that this should crash MATLAB, it might be worth while to submit a bug report. However, you would probably want to update the figure in the more efficient way, following the method I demonstrated above.
Note that this method can be used to update any of the graphical elements in a plot. For example, I have used this method to animate images.