MATLAB: How to Create a Static Legend for a Dynamic Axes

dynamic axeslegendsplotting performancescrolling data

I have written a GUI for interaction with and tracking of the Lorenz Attractor. The 3D plot is in the main figure, but the user can open a separate figure that displays the position-time graph for each coordinate direction. This component plot deletes the data from the graph handle as soon as it leaves the lower axis range to avoid consuming my memory (the data essentially scrolls across the axes). It currently has a very good running speed, but I cannot figure out how to add a legend to the component plot without slowing down performance. Even if I turn auto-update off and only create the legend for the first set of points plotted, it somehow still finds a way to slow down my program significantly as it continues to run. Is there a way to assign the legend initially and then make it entirely static, so it is essentially just an image overlaid on the axis?
Here is my code for the plotting loop that currently has the legend statement commented out
if true
%animation plotting loop
ch = 0;
ck = 0;
for i = 2:length(t)
if ~triggers.stop
triggers.i = i;
triggers.startPos.Update = [a(i, 1), a(i, 2), a(i, 3)];
h(i-ch) = plot3(ax1, a(i-1:i,1),a(i-1:i,2),a(i-1:i,3), linestyle, 'color', color);
if i > nTrim && nTrim ~= 0
delete(h(2))
h(2) = [];
ch = ch+1;
end
if triggers.comp && mod(i, 2) == 0 && i > kBuffer
xlim(ax3, [t(i)-tGRange, t(i)]);
ylim(ax3, [min(min(a)), max(max(a))]);
k(:, triggers.kk-ck) = plot(ax3, t(i-kBuffer:i), a(i-kBuffer:i, 1), '-k', t(i-kBuffer:i), a(i-kBuffer:i, 2), '-r', t(i-kBuffer:i), a(i-kBuffer:i, 3), '-c');
% if triggers.kk == 2
% legend(ax3, k(:,2), {'X Position', 'Y Position', 'Z Position'}, 'AutoUpdate','off')
% end
if k(1, 1).XData < t(i)-tGRange
delete(k(:, 1))
k(:, 1) = [];
ck = ck+1;
end
triggers.kk = triggers.kk + 1;
end
pause(pauseTime)
else %break statement for terminating program
break
end
end
triggers.stop = false;
end
end

Best Answer

  • Try setting the XData/YData/ZData properties of the plots rather than calling 'plot'/'plot3' each time in the loop. For example:
    close all;
    figure;
    ax = axes;
    px = plot(ax, 0, 0, 'x'); hold on;
    py = plot(ax, 0, 0, 'o');
    legend(ax, {'x dir', 'y dir'});
    deg = 0:720;
    xv = sind(deg);
    yv = cosd(deg);
    scope_width = 50;
    for i = deg+1
    range = i:min(numel(deg),i+50);
    px.XData = deg(range);
    px.YData = xv(range);
    py.XData = deg(range);
    py.YData = yv(range);
    xlim([px.XData(1), px.XData(1)+scope_width]);
    ylim([-1, 1]);
    pause(0.01);
    end