Why isn't my graph plotting?

 N=4;
 R=2;
 Phase=pi/4;

 theta=zeros(1,N);

    x1=R*cos(theta+Phase)/sqrt(2);
    y1=R*sin(theta+Phase)/sqrt(2);
    plot(x1,y1);
    fill(x1,y1,'k');
    hold;

    x2=R*cos(theta+Phase)/sqrt(2)+R;
    y2=R*sin(theta+Phase)/sqrt(2);
    plot(x2,y2);
    fill(x2,y2,'r');

The graph should show half of the screen black and the other half red but it just gives me a blank graph. What am I doing wrong?

Answer 1

[Walter Roberson]

All of your x1 are the same; all of your y1 are the same; all of your x2 are the same; all of your y2 are the same.

I would suggest to you that

   theta=zeros(1,N);

is not correct, that you should be using a vector of theta values from 0 to something or other. I suspect you want linspace()