how to plot a graph for all values of Cgd versus frequency??

A = load('C1_vd0_vg-5_a.txt')
size(A)
n = 191;
for i = 1:191 
A (i,:)
A([i] , [2 3 4 5 6 7 8 9])

freq = A (i,1)
s11mag = A(i,2)
s11ang = A(i,3)
s12mag = A(i,4)
s12ang = A(i,5)
s21mag = A(i,6)
s21ang = A(i,7)
s22mag = A(i,8)
s22ang = A(i,9)

%1deg = 0.0174532925 radians
q = 0.0174532925

s11real = s11mag * cos(s11ang * q)
s11img = s11mag * sin (s11ang * q)
s11 = s11mag.* exp( j * (s11ang * q))

s12real = s12mag * cos(s12ang * q)
s12imag = s12mag * sin (s12ang * q)
s12 = s12mag.* exp( j * (s12ang * q))

s21real = s21mag * cos(s21ang * q)
s21imag = s21mag * sin (s21ang * q)
s21 = s21mag.* exp( j * (s21ang * q))

s22real = s22mag * cos(s22ang * q)
s22imag = s22mag * sin (s22ang * q)
s22 = s22mag.* exp( j * (s22ang * q))

s = [s11 s12 ; s21 s22]
D = ((1+s11)*(1+s22)-s12*s21)
Z0 = 50

y11 = ((1-s11)*(1+s22)+s12*s21) / (D * Z0) 

y12 = -2*s12 / (D * Z0) 

y21 = -2*s21 / (D * Z0) 

y22 = ((1+s11)*(1-s22)+s12*s21) / (D * Z0) 

y = [y11 y12 ; y21 y22] 

y11real = real(y11)
y11imag = imag (y11)
y12real = real(y12)
y12imag = imag (y12)
y21real = real(y21)
y21imag = imag (y21)
y22real = real(y22)
y22imag = imag (y22)

%y12imag = -jw (Cgd)

Cgd = - y12imag /  (2 * pi * freq)

freq = [0:5:20];

plot(freq ,Cgd)
ylabel('Cgd')
xlabel('frequency')

end