Circumference and cone in plot3

Hello everyone!

How I represent a circumference in a figure of Plot3? (i have the coordinates x,y and z of center and radius).

By the way...how i represent a cone beginning in center of circumference (x,y,z of center)?

Thanks!!

Answer 1

[Star Strider]

See the documentation for the sphere and cylinder functions. You can define the radius of the cylinder as a function of z.

For instance:

r = 0:0.1:1;                % Define Radius Of Cone
[X,Y,Z] = cylinder(r);

figure(1)
surf(X, Y, Z)
axis square

[Nuno]

for example, to the circumference

hold on
r=9;
x=198;
y=145;
z=210;
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
zunit= r*sin(th)+z; % I'm not sure it
h = plot3(xunit, yunit,zunit);

is correct?

[Star Strider]

If that is what you want, then it’s correct. It plots the circumference of a circle on an inclined plane.

The cone is easy:

% CONE USING ‘plot3’
z = linspace(0, 100, 1000);
x = z.*cos(z*pi);
y = z.*sin(z*pi);

figure(1)
plot3(x, y, z)
grid on
axis equal

[Nuno]

Yeah, it s work!! :D

But if i want that cone begin in one specific point? i change linspace line?

[Nuno]

x0=170;
y0=186;
z0=210;
hold on
[x,y,z] = sphere;
surf(x+x0,y+y0,z+z0)

how i put the radius?

[Star Strider]

I am not sure what you want to do. You are of course free to experiment by changing the linspace parameters as you wish. If you want to shift the apex of the cone from (0,0), add those values to ‘x’ and ‘y’.

So to shift it to (10,10), do this:

z = linspace(0, 100, 1000);
x = z.*cos(z*pi)+10;
y = z.*sin(z*pi)+10;

figure(1)
plot3(x, y, z)
grid on
axis equal