How to plot the l2 norm circle?

Hi all,

I'm trying to visualize the l2 norm circle. It seems easy but I'm stuck. This is the code I write to plot the circle (based on x^2 + y^2 = 1):

clear; clc;

x = -1:0.01:1;
y = sqrt(1 - x .^ 2);

plot(x, y)

hold on

plot(y, x)

axis square

It gives me a figure like this:

apparently the left lower part is missing, what I do not understand is that both x and y are non-negative, why would l2 norm gives a full circle where left lower part is negative for both x and y?

Please forgive me if I did not explain mathematically enough.

Answer 1

[Torsten]

theta=0:2*pi/100:2*pi;
x=cos(theta);
y=sin(theta);
plot(x,y)

Best wishes

Torsten.

[Xh Du]

Hi Torsten,

Your code will plot the circle, but what is it to do with l2 norm?

[Torsten]

The circle with radius 1 around the origin is the set of points with l2norm=1.

I thought that you tried to plot this set of points, didn't you ?

Best wishes

Torsten.

[Xh Du]

Thanks for your answer. What I'd like to understand is how to plot the circle from function x^2 + y^2 = 1.

[Torsten]

clear; 
clc;

x = -1:0.01:1;
y = sqrt(1 - x .^ 2);

plot(x, y)

hold on

plot(x, -y)

axis square

Best wishes

Torsten.

[Xh Du]

Many thanks!