How do I get a graph to spiral

I'm working on creating a spiral of archimedes for a hw assignment, I'm having difficulty getting the plot to spiral properly. Right now I'm just getting a straight line. I cannot use polar plot either.

The code I have right now is:

clear variables
clc
x=linspace(0,40,2000);
k=1.5;
theta=0:(pi/8):(8*pi);
r=k*theta;
plot(theta,r)
grid on

this is what I'm ultimately supposed to be creating.

Answer 1

[DGM]

Well it would be a straight line, wouldn't it? Since there's a direct linear relationship between r and theta and that's what you're plotting.

r=k*theta;

It's only a spiral if you're looking at it from the right perspective.

clear variables
clc; clf
k=1.5;
theta=linspace(0,8*pi,1000);
r=k*theta;
x=r.*cos(theta);
y=r.*sin(theta);

plot(x,y)
axis equal
grid on

[Brendan Clark]

I had actually just figured that out with a combo of the previous answer and another help page I had open.

I'm glad you posted however, because I was in the process of trying to figure out how to make the axis equal, thank you for that!

Answer 2

[KSSV]

t = linspace(0,10*pi,5000);
r = 5. ;
c = 4 ; 
x = r*cos(t) ;
y = r*sin(t) ;
z = c*t ;
comet3(x,y,z) ;

plot3(x,y,z,'Color','m','Linewidth',1) ;
title({'Parametric Equations for Spiral';'x=rcos\theta';'y=rsin\theta';'z = c\theta'}) ;

[Brendan Clark]

That formatting was able to help me at least get a circle, but ultimately I'm trying to create a 2D archimedes sprial like the one pictured above.