Need help calculating thrust required curve

I need to calculate a thrust required curve for an aircraft to find the velocity at maximum lift-drag ratio. I keep getting errors; either it says that 'v' is undefined or that there aren't enough input arguments. No, I don't have a specific value for velocity, the curve is supposed to tell me that. Please help.

%initial data

function fval=TRc(v)

rho=1.225; %kg/m^3

s=47; %m^2

AR=6.5; %unitless

e=0.87; %unitless

w=103047; %N

cd0=0.032; %unitless

ET=40298; %N%engine thrust

PA=2*ET; %N

cl = (2*w)/(v^2*rho*s); %lift coefficient

cd=cd0+(cl^2/(pi*e*AR)); %drag coefficient

TR=w/(cl/cd); %N

PR=TR*v; %W

fval=(PA-PR)/w;

plot(v,fval);

end

Answer 1

[Torsten]

You must call TRc with a numerical input vector for v to get a plot.

v = linspace(1,20,100);
fval = TRc(v);
plot(v,fval)

function fval=TRc(v)
  rho=1.225;              %kg/m^3
  s=47;                   %m^2
  AR=6.5;                 %unitless
  e=0.87;                 %unitless
  w=103047;               %N
  cd0=0.032;              %unitless
  ET=40298;               %N%engine thrust
  PA=2*ET;                %N
  cl = (2*w)./(v.^2*rho*s); %lift coefficient
  cd=cd0+(cl.^2/(pi*e*AR)); %drag coefficient
  TR=w./(cl./cd);           %N
  PR=TR.*v;                %W
  fval=(PA-PR)./w;
end