How do I plot a circle with a given radius and center and i need to extract x,y,z points

i know to extract x,y using

th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;

but how will i get z co-ordinate if i need to plot one 3d circle.

Answer 1

[Star Strider]

The circle you described is two-dimensional. The ‘z’ coordinate is uniformly 0. If you want a circle above the plane, just define a new variable ‘zunit’ and define a vector to define it. This code puts the circle at z=5:

r = 1.25;
x =  0.1;
y = -0.1;

th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
zunit = 5*ones(size(th));

figure(1)
plot3(xunit, yunit, zunit)
grid on
axis([-1.5  1.5    -1.5  1.5    0  10])

[Rudranarayan Kandi]

Very nice!!! Can you plot a 3D circle on a triangular plane with x,y and z intercepts ??? radius and centre of the circle is known. Please help

Answer 2

[rajath mavathur basavaraj]

thank you very much it really helped me to understand the working of xyz plane.

[Star Strider]

My pleasure.

If you want to incline the circle (instead of having it flat), use this for ‘zunit’:

zunit = 2.5 + 2.5*sin(th-pi);           % Inclined Circle

Experiment with it, and with various other functions in ‘zunit’, and observe the effects. The only constraint is that they all have to be the same size as (or functions of) your ‘th’ variable.