how to make circle in matlab and generate random points inside it

Question

hello i want to ask a question how to make a circle in matlab and mark its center and g

Answer 1

Here's another option:

%// Set parameters
R = 0.5;   %// radius
C = [3 4]; %// center [x y]
N = 50;    %// number of points inside circle

%// generate circle boundary
t = linspace(0, 2*pi, 100);
x = R*cos(t) + C(1);
y = R*sin(t) + C(2);

%// generate random points inside it
th = 2*pi*rand(N,1);
r  = R*rand(N,1);

xR = r.*cos(th) + C(1);
yR = r.*sin(th) + C(2);

%// Plot everything
figure(1), clf, hold on
plot(x,y,'b')
plot(C(1),C(2),'r.', 'MarkerSize', 100)
plot(xR,yR,'k.')
axis equal

Here's why that could be useful:

%// Set parameters
R = 0.5;     N = 50;
C = [3 4];   M = 100;  %// points on boundary

%// generate all points at once
t  = linspace(0, 2*pi, M)';
th = 2*pi*rand(N,1);
r  = R*rand(N,1);
xR = [R*ones(M,1); r] .* cos([t; th]) + C(1);
yR = [R*ones(M,1); r] .* sin([t; th]) + C(2);

%// Plot everything
figure(1), clf, hold on
plot(xR(1:M),yR(1:M),'b')                %// circle boundary
plot(C(1),C(2),'r.', 'MarkerSize', 100)  %// center
plot(xR(M+1:end),yR(M+1:end),'k.')       %// random points
axis equal