How to stop the axes from changing within loop without defining them every iteration

Question

Magnus Sejer Lind 2022-3-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1673934-how-to-stop-the-axes-from-changing-within-loop-without-defining-them-every-iteration

评论： Voss 2022-3-17

I would like the decrease the running time of my code, setting the axes takes up a lot of time. How do a fix the axes, having then within the given limits and being equal without having to define them in every iteration of the for loop.

clc,clear variables, close all
h = 0.01;
t = 0:h:2; % Time
% Initial conditons
y0 = 2;
x0 = 5;
dydt0 = 5;
dxdt0 = 7;
Y0 = [y0 x0 dydt0 dxdt0];
% Solve system
Y = RK4_ODEs(@dYdt_ball,Y0,t);
Ysol = Y(:,1);
Xsol = Y(:,2);
% Motion plot
hf = figure(1);
for i = 1:length(Y)
    plot(Xsol(i),Ysol(i),'r.',MarkerSize=30)
    hold on
    rectangle('Position',[-0.1 -0.1 10.2 4.9])
    ht = text(4.4,5,'',Interpreter='latex');
    ht.String = ['t = ' num2str(t(i),5) '\ s'];
    hold off
    axis equal             % Slow
    axis([-1 11 -1 6])     % Slow
    title('Motion of Ball in Box')
    
    pause(0.001)
end

Thank you

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Answer 1

Voss 2022-3-17

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https://ww2.mathworks.cn/matlabcentral/answers/1673934-how-to-stop-the-axes-from-changing-within-loop-without-defining-them-every-iteration#answer_920194

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You can set up the axes once, and also create the objects in the axes once (i.e., the line representing the ball, the text for the time, and the rectangle). Then update those objects' properties as needed inside the loop. This way the axes doesn't need to change at all within the loop.

clc,clear variables, close all
h = 0.01;
t = 0:h:2; % Time
% Initial conditons
y0 = 2;
x0 = 5;
dydt0 = 5;
dxdt0 = 7;
Y0 = [y0 x0 dydt0 dxdt0];
% Solve system
Y = RK4_ODEs(@dYdt_ball,Y0,t);
Ysol = Y(:,1);
Xsol = Y(:,2);
hf = figure(1);
axis equal
axis([-1 11 -1 6])
title('Motion of Ball in Box')
ball_line = line( ...
    'Parent',gca(), ...
    'XData',[], ...
    'YData',[], ...
    'LineStyle','none', ...
    'Color','r', ...
    'Marker','.', ...
    'MarkerSize',30);
rectangle('Position',[-0.1 -0.1 10.2 4.9]);
ht = text(4.4,5,'','Interpreter','latex');
% Motion plot
for i = 1:length(Y)
    set(ball_line,'XData',Xsol(i),'YData',Ysol(i));
    ht.String = ['t = ' num2str(t(i),5) '\ s'];
    drawnow();
end

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Magnus Sejer Lind 2022-3-17

Works Great!

Thank you!

Voss 2022-3-17

You're welcome!

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Answer 2

David Hill 2022-3-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1673934-how-to-stop-the-axes-from-changing-within-loop-without-defining-them-every-iteration#answer_920204

在 MATLAB Online 中打开

Why not just move it outside the loop?

hf = figure(1);
hold on
rectangle('Position',[-0.1 -0.1 10.2 4.9])
for i = 1:length(Y)
    plot(Xsol(i),Ysol(i),'r.',MarkerSize=30)
    ht = text(4.4,5,'',Interpreter='latex');
    ht.String = ['t = ' num2str(t(i),5) '\ s'];
end
axis equal             
axis([-1 11 -1 6])     
title('Motion of Ball in Box')