MATLAB: Plotting the solution of multi-variable non-linear equations (solved using fsolve).

fsolveMATLABplot

These are the equations:
function [fval]= ptfunc(X)
Tcell=X(1);
Pcell=X(2);
Qh=X(3);
Pteg=X(4);
alpha = 0.95;
A = (0.04)^2; 
epsilon = 0.88; 
sigma = 5.69*10^(-8); 
Ta = 298.15; 
u=(0.003+1/5)^-(1);
ns = 0.10; 
theta = 0.0011; 
An=6.4*10^-7;
Hn=0.01;%:0.01:0.06;
N=62;
S=185*10^-6;
rho=10^-5;
den=2*rho;
k=1.5;
Z=(S^2)/(rho.*k);
Tc=298;
r=0.2;
n=0.0001;
hc=0.00009;
num2=2*r*hc;
G=500;
fval(1,1)= -Qh+ alpha*G*A-u*A*(Tcell-Ta)-epsilon*sigma*A*((Tcell.^4)-(Ta^4))-Pcell;
fval(2,1)= -Pcell+ alpha*G*A*ns.*(1-theta.*(Tcell - 298));
fval(3,1)= -Qh + (k*An*N/Hn)*(1-Z*(3*Tcell+Tc)/8)*(Tcell-Tc);
fval(4,1)= -Pteg+(S^2)*An*N*((Tcell-Tc)^2)./(den.*(n+Hn).*(1+num2./Hn).^2);
I need to plot the varaibles with respect to G. How do I do that?

Best Answer

function main
  G = linspace(250,750).';
  X0 = [1,1,1,1];
  for i=1:numel(G)
    sol = fsolve(@(X)ptfunc(X,G(i)),X0);
    x(i,:) = sol;
    X0 = sol;
  end  
  plot(G,x(:,1))
end
function fval = ptfunc(X,G)
  Tcell=X(1);
  Pcell=X(2);
  Qh=X(3);
  Pteg=X(4);
  alpha = 0.95;
  A = (0.04)^2; 
  epsilon = 0.88; 
  sigma = 5.69*10^(-8); 
  Ta = 298.15; 
  u=(0.003+1/5)^-(1);
  ns = 0.10; 
  theta = 0.0011; 
  An=6.4*10^-7;
  Hn=0.01;%:0.01:0.06;
  N=62;
  S=185*10^-6;
  rho=10^-5;
  den=2*rho;
  k=1.5;
  Z=(S^2)/(rho.*k);
  Tc=298;
  r=0.2;
  n=0.0001;
  hc=0.00009;
  num2=2*r*hc;
  %G=500;
  fval(1,1)= -Qh+ alpha*G*A-u*A*(Tcell-Ta)-epsilon*sigma*A*((Tcell.^4)-(Ta^4))-Pcell;
  fval(2,1)= -Pcell+ alpha*G*A*ns.*(1-theta.*(Tcell - 298));
  fval(3,1)= -Qh + (k*An*N/Hn)*(1-Z*(3*Tcell+Tc)/8)*(Tcell-Tc);
  fval(4,1)= -Pteg+(S^2)*An*N*((Tcell-Tc)^2)./(den.*(n+Hn).*(1+num2./Hn).^2);
end
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