How can I show this shape moving along the trajectory?

Question

Mikey 2014-5-10

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/129072-how-can-i-show-this-shape-moving-along-the-trajectory

回答： Eugene 2014-5-12

This only generates the projectile at the end of the trajectory. The shape should start at (0,20) and end at (20,100)and scale from 100% to 25%

function v = problem1

% coordinates of square under one variable square = [0, 4, 4, 0;0, 0, 4, 4];

% generate animation window figure

xmin = -5;

xmax = 25;

ymin = -5;

ymax = 125;

axis equal

axis([xmin xmax ymin ymax])

hold on

%setting your trajectory

t = linspace(0,20,500); % independent variable of your function

trajectory = 1/4*t.^2; % represents y in y = t^2

scale = .99;

    for i = 500
% object moving along projectile
    h = fill(square(1,:) + t(i),square(2,:) + trajectory(i),'r');
    hold on;
% scales the figure from 100% to 25%
        fill(scale*square(1,:) + t(i), scale*square(2,:) + trajectory(i), 'r');
    hold on;
         % do not change below 2 lines, should follow your fill command
         v.x(i,:)=get(h,'xdata')';
         v.y(i,:)=get(h,'ydata')';
    pause(.3)
    end

end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Jan 2014-5-10

编辑：Jan 2014-5-10

Please describe the problems you have with the shown code.

What does "scales the figure from 100% to 25%" mean?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Eugene 2014-5-12

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/129072-how-can-i-show-this-shape-moving-along-the-trajectory#answer_136456

在 MATLAB Online 中打开

1. your for loop definition should be

i=1:500

2. you didn't have an algorithm to change the value of scale.

3. scale will not work to shrink the size of the square (i'm assuming that is what you're tyring to do) because the original coordinates do not put the centroid of the square at zero.

Try this:

square = [-2, 2, 2, -2;-2, -2, 2, 2];
figure;
xmin = -5;
xmax = 25;
ymin = -5;
ymax = 125;
axis equal
axis([xmin xmax ymin ymax])
hold on
N = 50;
t = linspace(0,20,N); 
trajectory = 1/4*t.^2;
scale = linspace(1,0.25,N);
for i = 1:N
    % object moving along projectile
    h = fill(square(1,:) + t(i),square(2,:) + trajectory(i),'r');
    hold on;
    % scales the figure from 100% to 25%
    fill(scale(i)*square(1,:) + t(i), scale(i)*square(2,:) + trajectory(i), 'r');
    hold on;
    pause(0.3)
end

Otherwise if you don't want to have a persistent image then just change the x and y data for the filled object.

square = [-2, 2, 2, -2;-2, -2, 2, 2];
figure;
xmin = -5;
xmax = 25;
ymin = -5;
ymax = 125;
axis equal
axis([xmin xmax ymin ymax])
hold on
N = 50;
t = linspace(0,20,N); 
trajectory = 1/4*t.^2;
scale = linspace(1,0.25,N);
h1 = fill(square(1,:) + t(1),square(2,:) + trajectory(1),'r');
h2 = fill(scale(1)*square(1,:) + t(1), scale(1)*square(2,:) + trajectory(1), 'r');
for i = 2:N
    % object moving along projectile
    set(h1,'XData',square(1,:) + t(i),'YData',square(2,:) + trajectory(i));
    hold on;
    % scales the figure from 100% to 25%
    set(h2,'XData',scale(i)*square(1,:) + t(i),'YData',scale(i)*square(2,:) + trajectory(i));
    hold on;
    pause(0.3)
end