Error using fzero (line 184) FUN must be a function, a valid character vector expression, or an inline function object. What is the issue here?

vi = 600;

v = 0:0.01:1000;

sig = input('Input sigma value: ');

w = input('Input weight of airfoil: ');

f = @(v) 0.01*sig*v.^2 + (0.95/sig)*((w.^2)./(v.^2));

fvi = f(vi);

root = fzero(fvi, vi)

I have no idea why I'm encountering this error, can someone please help me.

[Broden Tripcony]

Actually nvm I made a silly mistake, this does not cross the x axis, its derivative does. got confused my bad.

Answer 1

[Jan]

v is the variable of the function. You do not have to deine it as a vector.

fzero expects a function handle, but f(vi) is a number.

vi  = 600;
sig = input('Input sigma value: ');
w   = input('Input weight of airfoil: ');
f   = @(v) 0.01*sig*v.^2 + (0.95/sig)*((w.^2)./(v.^2));
root = fzero(f, vi)

[Broden Tripcony]

Yeah I realised this too, fixed it up a few hours ago:

vi = 500;

sig = input('Input sigma value: ');

w = input('Input weight of airfoil: ');

f = @(v) 0.02*sig*v - (1.90/sig)*((w^2)/(v^3)); %deriv. of Drag Eqn

dfdv = @(v) 0.02*sig + (5.70/sig)*((w^2)/(v^4)); %double deriv. of Drag Eqn

fvi = f(vi);

mi = dfdv(vi);

while abs(fvi) > 0

vi_new = vi - fvi/mi;

vi = vi_new

fvi = f(vi);

mi = dfdv(vi);

end

root = fzero(f, 600)