How can I generate the data for an eight '8' draw?

Question

jadaslg 2013-6-13

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https://ww2.mathworks.cn/matlabcentral/answers/78918-how-can-i-generate-the-data-for-an-eight-8-draw

回答： Carmelo Fabrizio Blanco 2020-11-3

Hello, I would like to know how to generate the data for the shape of an eight. I've been trying with some hysteresis functions but nothing gets me close really.

Thank you very much

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Answer 1

David Sanchez 2013-6-13

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https://ww2.mathworks.cn/matlabcentral/answers/78918-how-can-i-generate-the-data-for-an-eight-8-draw#answer_88654

在 MATLAB Online 中打开

You can try with this:

t=0:.1:2*pi;
x = -sin(t);
y = sin(t);
plot(t,x,'*',t,y,'+')

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David Sanchez 2013-6-13

在 MATLAB Online 中打开

To see the 8 shape:

plot(x,t,'*',y,t,'+')

jadaslg 2013-6-13

Thank you very much! It's kind of what I wanted.

Is there any easy way to extract the x and y datapoints for this figure?

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Answer 2

Paulo Barbosa 2016-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/78918-how-can-i-generate-the-data-for-an-eight-8-draw#answer_234793

在 MATLAB Online 中打开

div = pi/50;       % Resolution
sz = 100;          % Number of Points in 2 Pi
th = zeros(1,sz);
th(1) = pi;        % Starting at (0,0) and going up.
for i = 2:sz
    th(i) = th(i-1)-div;
end
circ_x = fat*cos(th);
circ_y = fat*sin(th);
x1 = circ_x(1:26);
y1 = circ_y(1:26);
% -------------------------------------------
th(1) = 0;
for i = 2:sz*fat
    th(i) = th(i-1)+div*fat;
end
cos_x = th;
cos_y = fat*cos(th/fat);
x2 = cos_x(1:51);
y2 = cos_y(1:51);
% -------------------------------------------
th(1) = -pi/2;
for i = 2:sz
    th(i) = th(i-1)+div;
end
circ_x = fat*cos(th);
circ_y = fat*sin(th);
x3 = circ_x(1:51)+16;
y3 = circ_y(1:51);
% -------------------------------------------
x4 = x2';
x4 = flipud(x4);
x4 = x4';
y4 = y2';
y4 = flipud(y4);
y4 = -y4';
% -------------------------------------------
th(1) = -pi/2;
for i = 2:sz
    th(i) = th(i-1)-div;
end
circ_x = fat*cos(th);
circ_y = fat*sin(th);
x5 = circ_x(1:26);
y5 = circ_y(1:26);
% -------------------------------------------
x = [x1 x2 x3 x4 x5];
y = [y1 y2 y3 y4 y5];
% A plot so you can see each section
figure
hold on
plot(x1,y1,'.r');
plot(x2,y2,'.b');
plot(x3,y3,'.k');
plot(x4,y4,'.g');
plot(x5,y5,'.y');