Making animatedlines that dynamically change linestyle depending on conditions

Question

Jonathan Ward 2021-2-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/754459-making-animatedlines-that-dynamically-change-linestyle-depending-on-conditions

编辑： Jonathan Ward 2021-2-24

I have been trying to make a 2D boid simulation with the animatedline command in a 'wrapped universe'. To do so, I used mod(point,xsize) to wrap my birbs if the new position after a timestep brought it outside the 'bounds' of the universe. The issue I have is that when using animatedline, my addpoint command joins the position of the current timestep with the previous one when it gets 'wrapped'.

This results in horizontal and vertical lines on the screen. I do not want these lines and I do not believe each addpoint() can designate the style of each line connecting the points, otherwise I would use linestyle 'none' for those points.

How can I achieve a similar solution to the code below without animatedline's inability to have dynamic linestyle changes? I know MATLAB has toolbox for boid simulations, but I really really wanted one of my own.

%% Make universe and variables
xsize = 100;
ysize = 100;
%zsize = 100;
timesteps = 100000;
stepsize = 0.01;
nbirbs = 50;
h = animatedline;
axis = ([0 xsize 0 ysize]);
%% Make birb tracker with positions and velocity
for i=1:nbirbs
    birbs(i).al = animatedline;
    birbs(i).xy = zeros(timesteps,2); % Position in [m]
    birbs(i).v = zeros(timesteps,2); % Velocity in [m]/[s]
    
    %initial values of positon and velocity
    birbs(i).xy(1,:) = xsize*rand(1,2); 
    
    temptheta = 2*pi*rand;
    birbs(i).v(1,:) = [cos(temptheta) sin(temptheta)];
end
    
%% Iterate birb tracker and plot as we go
    addpoints(birbs(1).al,birbs(1).xy(1,1),birbs(1).xy(1,2)); %Add initial points
for i = 2:timesteps % Find new positions and plot
    for bird = 1:nbirbs    
        birbs(bird).xy(i,:) = mod(birbs(bird).xy(i-1,:) + stepsize*birbs(bird).v(1,:),xsize); %Find new birb position at next timestep
        addpoints(birbs(bird).al,birbs(bird).xy(i,1),birbs(bird).xy(i,2)); %Add the point to the animated line for that birb
        
    end
    drawnow limitrate % Draw every birb's position after each TIMESTEP
end
drawnow %Idk what this is doing

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Answer 1

Steven Lord 2021-2-24

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/754459-making-animatedlines-that-dynamically-change-linestyle-depending-on-conditions#answer_631734

在 MATLAB Online 中打开

h = animatedline('LineStyle', '-');

axis([0 360 -1 1])

for x = 0:360

if mod(x, 30) == 0

addpoints(h, NaN, NaN);

else

addpoints(h, x, sind(x))

end

xline(150, 'r')

If you were to zoom in, you'd see the red line at x = 150 is exactly inside the gap created by the NaN value I added to break the line when x was 150.

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Jonathan Ward 2021-2-24

编辑：Jonathan Ward 2021-2-24

Thank you Steven, this was exactly what I was looking for! I had no idea NaN was a thing, have a great evening! I set the condition for a NaN point when the distance between the point i and i-1 was >95. then i plot i-1 with i by pretend i-1 was 'wrapped' to make it look perfectly normal. cheers!

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