I keep getting the "not enough inputs error" and I don't know how to fix it

global m1 m2 w1a w1w w1m w2m w2w w2a

m1 = 135;

m2 = 30.3455;

w1a = .220;

w1w = .780;

w1m = .000;

w2m = .202;

w2w = .798;

w2a = .000;

function F = Control_volume_4(x)

global m1 m2 w1a w1w w2m w2w

% x(1) = w1m

% x(2) = w2a

% x(3) = w3a

% x(4) = w3m

% x(5) = w3w

% x(6) = m3

F(1) = w1a + x(1) + w1w;

F(2) = x(2) + w2m + w2w;

F(3) = x(3) + x(4) + x(5) - 1;

F(4) = m1 * w1a + m2 * x(2) - x(6) * x(3);

F(5) = m1 * x(1) + m2 * w2m - x(6) * x(4);

F(6) = m1 * w1w + m2 * w2w - x(6) * x(5);

end

guess4 = zeros(1,6);

answer_CV4 = fsolve(Control_volume_4, guess4);

disp(answer_CV4)

i get the " not enough input arguments " error pointing at the x(1) in the F(1) equation

Answer 1

[Stephen23]

"i get the " not enough input arguments " error pointing at the x(1) in the F(1) equation"

That error is caused by the fact that you called Control_volume_4 (without any input arguments) rather than providing a function handle to FSOLVE: What you did:

answer_CV4 = fsolve(Control_volume_4, guess4);

% ^^^^^^^^^^^^^^^^ here you *call* the function

What you should have done (as shown in the FSOLVE documentation):

answer_CV4 = fsolve(@Control_volume_4, guess4);

% ^ define a function handle, does not *call* the function

See: https://www.mathworks.com/help/optim/ug/fsolve.html

https://www.mathworks.com/help/matlab/matlab_prog/creating-a-function-handle.html

After fixing that you will likely need to fix some other errors. You should also avoid GLOBAL:

m1 = 135;
m2 = 30.3455;
w1a = 0.220;
w1w = 0.780;
w1m = 0.000;
w2m = 0.202;
w2w = 0.798;
w2a = 0.000;
fnh = @(x) Control_volume_4(x,m1,m2,w1a,w1m,w1w,w2a,w2m,w2w);
out = fsolve(fnh, zeros(1,6));

Solver stopped prematurely.

fsolve stopped because it exceeded the function evaluation limit,
options.MaxFunctionEvaluations = 6.000000e+02.

format short G
disp(out)

     -0.99135     -0.97324      -128.38       -19842        19971    0.0064546

function F = Control_volume_4(x,m1,m2,w1a,w1m,w1w,w2a,w2m,w2w)
F = nan(1,6);
F(1) = w1a + x(1) + w1w;
F(2) = x(2) + w2m + w2w;
F(3) = x(3) + x(4) + x(5) - 1;
F(4) = m1 * w1a  + m2 * x(2)  - x(6) * x(3);
F(5) = m1 * x(1)  + m2 * w2m  - x(6) * x(4);
F(6) = m1 * w1w  + m2 * w2w  - x(6) * x(5);
end

Answer 2

[Torsten]

m1 = 135;
m2 = 30.3455;
w1a = .220;
w1w = .780;
w1m = .000;
w2m = .202;
w2w = .798;
w2a = .000;
syms x [6 1];
F(1) = w1a + x(1) + w1w;
F(2) = x(2) + w2m + w2w;
F(3) = x(3) + x(4) + x(5) - 1;
F(4) = m1 * w1a  + m2 * x(2)  - x(6) * x(3);
F(5) = m1 * x(1)  + m2 * w2m  - x(6) * x(4);
F(6) = m1 * w1w  + m2 * w2w  - x(6) * x(5);
xsol = solve(F==0)

xsol = struct with fields:
    x1: -1
    x2: -1
    x3: -22711512183341056/569
    x4: -4534217384621546375/569
    x5: 4556928896804888000/569
    x6: 569/35184372088832000

double(xsol.x1)

ans = -1

double(xsol.x2)

ans = -1

double(xsol.x3)

ans = -3.9915e+13

double(xsol.x4)

ans = -7.9687e+15

double(xsol.x5)

ans = 8.0087e+15

double(xsol.x6)

ans = 1.6172e-14