How to normalize electrical field into antenna gain?

Gain pattern

I want to draw the gain pattern of uniform linear array and uniform circular array. But I don't know how to normalize electrical field into antenna gain.
Here is my MATLAB code in UCA.

E0 = 1;
theta_0 = 90/180*pi;
phi_0 = 0/180*pi;
N = 8;
lambda = 1;
d = lambda/2;
a = d*(N/2/pi);
k = 2*pi/lambda;
phi = 0.01:0.01:2*pi;
theta = 0.01:0.01i;
E = zeros(length(theta),length(phi));
for it = 1:1:length(theta)
for it2 = 1:1:length(phi)
for it3 = 1:1:N

alfa = -k*a*sin(theta_0)*cos(phi_0-2*pi*it3/N);
E(it,it2) = E(it,it2) + E0*exp(j*k*a*sin(theta(it))*cos(phi(it2)-2*pi*it3/N)
+ j*alfa);
end
end
end

G = E(157,: );
F = abs(G).^2;
figure
polar(phi,F,'-b');

I use the electrical field formula from the book, but I don't really know how to normalize it into gain pattern.

Re: Gain pattern

normalization is setting your max to 1.so the antenna gain would be divided by max gain.

regards.
sajid mohammed.