# How do I get a graph to spiral

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Brendan Clark on 6 Apr 2021
Commented: Brendan Clark on 6 Apr 2021
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. DGM on 6 Apr 2021
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 on 6 Apr 2021
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!

KSSV on 6 Apr 2021
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 on 6 Apr 2021
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.