Asked by Eleni agou
on 16 Sep 2018

Hi,

I drawn a circle on matlab with parametric equations. I give the xcenter,ycenter,r(x1,y1,r1) and the s.S is the number of points which equidistant(have the same distance on circle). I drawn some points on circle and I want to draw 4 random points around. My code is:

t1 = 0:(pi/(5*s1)):2*pi; % s1 is the number of points I want

x1unit = r1 * cos(t1) + x1;

y1unit = r1 * sin(t1) + y1;

a1=x1unit(1:10:s1*10); %points around on circle

b1=y1unit(1:10:s1*10);

plot(x1unit, y1unit, 'b', x1, y1, 'ok');%circle

plot(a1, b1, 'o');

I want random points on circle 3 ,4,or 5 or more on circle.But I couldn't to success it , yes. Could you help me?

Thanks in andvance,

Answer by Image Analyst
on 16 Sep 2018

Edited by Image Analyst
on 16 Sep 2018

Accepted Answer

Try this:

% Plot a circle.

angles = linspace(0, 2*pi, 720); % 720 is the total number of points

radius = 20;

xCenter = 50;

yCenter = 40;

x = radius * cos(angles) + xCenter;

y = radius * sin(angles) + yCenter;

% Plot circle.

plot(x, y, 'b-', 'LineWidth', 2);

% Plot center.

hold on;

plot(xCenter, yCenter, 'k+', 'LineWidth', 2, 'MarkerSize', 16);

grid on;

axis equal;

xlabel('X', 'FontSize', 16);

ylabel('Y', 'FontSize', 16);

% Now get random locations along the circle.

s1 = 5; % Number of random points to get.

randomIndexes = randperm(length(angles), s1)

xRandom = x(randomIndexes);

yRandom = y(randomIndexes);

plot(xRandom, yRandom, 'ro', 'LineWidth', 2, 'MarkerSize', 16);

Image Analyst
on 16 Sep 2018

Eleni's "Answer" moved here since it's not an answer to the original post, but a reply to mine:

thank you,

but I want the new random points and the s1 points. In this way, I have only the new random points.

a1=x1unit(1:10:s1*10); %points around on circle

b1=y1unit(1:10:s1*10);

Here is the code with equals points on circle

Image Analyst
on 16 Sep 2018

Eleni agou
on 16 Sep 2018

yes!!

thank you for your time

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