How to plot a graph using if function

Hi i am trying to plot a graph but not sure how to go about it. I want to plot a graph from my code of e against q where the value for absL(1) <= 1 is a shaded region or at least creates the boarder. this is my code so far i think i would use if function but not sure.

syms e q L
c= 1;
f(t)=(e-(2*q)*cos(2*t));

M=[0 1; -f(t) -c];
%*[x1; x2];
N=trace(M);
P=det(M);

(L^2)-(N*L)+P==0;

L(1) = (N+sqrt((N^2)-(4*P)))/2;
L(2) = (N-sqrt((N^2)-(4*P)))/2;

if abs(L(1)) <= 1
    

Answer 1

[Adam Danz]

I don't see any plotting commands so I don't know what kind of plot you're trying to create.

The problem can likely be solved by indexing. Spend some time on that page. Indexing is one of the main features of matlab.

For example,

idx = abs(L) <= 1; 
plot(q(idx),e(idx), 'ro')
hold on  
plot(q(~idx),e(~idx), 'bo')