Plotting 3D parameterised curve help

Question

Jenny Briggs 2016-3-14

编辑： Star Strider 2016-3-14

I want to plot the curve:

r(r, θ) = (rcos(θ), rsin(θ), θ), 0 ≤ r ≤ 1, 0 ≤ θ ≤ 2π.

But I'm not really sure how to go about it.

I have tried this:

r = linspace(0,1);

theta = linspace (0,2.*pi);

x = r*cos(theta);

y = r*sin(theta);

z = theta;

plot(x,y,z)

However it keeps resulting in error.

Any help would be greatly appreciated, thanks

Answer 1

Star Strider 2016-3-14

编辑：Star Strider 2016-3-14

Since ‘r’ and ‘theta’ have the same number of elements (by default 100 with linspace), you can use element-wise multiplication:

r = linspace(0,1);
theta = linspace (0,2*pi);
x = r.*cos(theta);
y = r.*sin(theta);
z = theta;
figure(1)
plot3(x, y, z)
grid on

That should do what you want (plot an Archimedes spiral).