A function to draw a circle with only radius as parameter?

Hello I need help to create a function that will help me draw a circle with a given radius.

So the function can only have the radius as parameter.

For example if I type draw_circle(5) I want to have a plot of a circle with radius 5. Since the equation is y^2+x^2=r^2 ---> y=+/-sqrt(r^2-x^2) it feels like I need two parameters in the function one for x and one for r.

So basically can someone help me construct a function draw_circle(r) that plots a circle with radius 5.

Thanks!

Answer 1

[Azzi Abdelmalek]

function cercle(r)
x=-r:.01:r
y=sqrt(r^2-x.^2)
hold on;
plot(x,y);
plot(x,-y)

call the function

 cercle(5)

[Peter]

I can't seem to get it to work

function circle(r) 
x=-r:.01:r 
y=sqrt(r^2-x.^2) 
hold on; 
plot(x,y); 
plot(x,-y) 
circle(5) 
end

it returns: "not enough input arguments in line2" should I call the function without end?

[Azzi Abdelmalek]

What circle(5) is doing inside a function?

save the function I writted above, it does'nt contain circle(5) . then in matlab command type

 circle(5)

[Peter]

Sorry I have been programming in python too much. Thank you it worked.

Answer 2

[Matt Fig]

function [] = plot_circle(R)
% Plots a circle of radius R
[X,Y] = cylinder(R,1000);
plot(X(1,:),Y(1,:))
axis equal

Save this as plot_circle.m then call from the command line:

plot_circle(4)  % Radius 4

If you just want a function handle that can do it, try this one:

f = @(R) plot(R*cos(0:.001:2*pi),R*sin(0:.001:2*pi));
f(3)
axis equal

Answer 3

[Image Analyst]

Have you read the FAQ yet? http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F