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

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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.

Accepted Answer

Star Strider
Star Strider on 8 Nov 2015
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])
  1 Comment
Rudranarayan Kandi
Rudranarayan Kandi on 11 Sep 2018
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

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More Answers (1)

rajath mavathur basavaraj
thank you very much it really helped me to understand the working of xyz plane.
  1 Comment
Star Strider
Star Strider on 8 Nov 2015
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.

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