MATLAB: How to plot the functions in the code according to theta

plotvariable

Here is my code.
clear all
format long
tic
N_cut=20;
eps0=(10^-9)/(36*pi);
mu0=4*pi*10^-7;
epsr1=1.;
epsr2=2.;
mur1=1.;
mur2=1.;
eps1=epsr1*eps0;
eps2=epsr2*eps0;
mu1=mur1*mu0;
mu2=mur2*mu0;
freq=299.7925*10^6;
omeg=2*pi*freq;
k=omeg*sqrt(eps1*mu1);
lambda=2*pi/k;
phi=45;
R=1.1;
for n=1:N_cut
      bes_kur1(n)=sqrt(pi.*k.*R./2).*besselj(n+0.5,k.*R);
      han_kur1(n)=sqrt(pi.*k.*R./2).*besselh(n+0.5,2,k.*R);
      bes_kur_der1(n)=-n.*sqrt(pi.*k./(2.*R)).*besselj(n+0.5,k.*R)+k.*sqrt(pi.*k.*R./2).*besselj(n-0.5,k.*R);
      han_kur_der1(n)=-n.*sqrt(pi.*k./(2.*R)).*besselh(n+0.5,2,k.*R)+k.*sqrt(pi.*k.*R/2).*besselh(n-0.5,2,k.*R);
      han_kur_dd(n)=sqrt(pi.*k.*R./2).*besselh(n+2.5,2,k.*R)-sqrt(pi./(2.*k.*R)).*(2.*n+3).*besselh(n+1.5,2,k.*R)+sqrt(pi./(2.*(k.*R).^3)).*...
              n.*(n+1).*besselh(n+0.5,2,k.*R);
       a(n)=(1i.^(-n)).*(2.*n+1)./(n.*(n+1));
       b(n)=(-a(n)).*bes_kur_der1(n)./han_kur_der1(n);
       c(n)=(-a(n)).*bes_kur1(n)./han_kur1(n);
          L1=legendre(n,cosd(theta));
          L11=legendre(n-1,cosd(theta));
          L2(n)=L1(2);
          if n==1
          L3(n)=0.;
          else
          L3(n)=L11(2);
          end
      L2_der(n)=(-(n+1).*L3(n)+n.*cosd(theta)).*L2(n)/sind(theta);
      E_r=((-1i.*cosd(phi).*b(n).*L3(n).*(han_kur_dd(n)+han_kur1(n))));
      E_theta=(cosd(phi)./(k.*R)).*((1i)*b(n)*han_kur_der1(n).*sin(theta).*L2_der(n)-c(n).*han_kur1(n)*(L3(n)./sin(theta)));
      E_phi=(sin(phi))./(k.*R).*(((1i).*b(n).*han_kur_der1(n).*(L3(n)./(sin(theta))))-(c(n).*han_kur1(n).*sin(theta)).*L2_der(n));
end
F_Er=sum(E_r);
F_Etheta=sum(E_theta);
F_Ephi=sum(E_phi);
figure
plot(theta,abs(F_Er)),grid on
hold
figure
plot(theta,abs(F_Etheta)),grid on
hold
figure
plot(theta,abs(F_Ephi)),grid on
hold

Best Answer

At the beginning of the code, put in
syms theta
then before you go to plot, you need to choose specific theta to plot for, such as by
Thetas = linspace(0, 2*pi, 100);
val_F_Er = double( subs(F_er, theta, Thetas) );
val_F_Etheta = double( subs(F_Etheta, theta, Thetas) );
val_F_Ephi = double( subs(F_Ephi, theta, Thetas) );
figure
plot(Thetas, abs(val_F_Er));
figure
plot(Thetas, abs(val_F_Etheta));
figure
plot(Thetas, abs(val_F_Ephi));
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