matrix size error using fsolve

I'm trying to use fsolve to solve a nonlinear system of equations but i keep getting the following error:

In an assignment A(I) = B, the number of elements in B and I must be the same.

All the globally defined variables are scalars. Here's my code:

function f = solvefeedgases(m)
global Cb Cc Ce HH2 HCH4 q xH2

f(1) = xH2 - (m(1)/(m(1) + m(2) + Cb + Cc + 2*Ce));
f(2) = m(3) - (m(2)/(m(1) + m(2) + Cb + Cc + 2*Ce));
f(3) = m(3) - m(4)*HCH4;
f(4) = -m(5) + m(1) + 2*Ce + Cc*q;
f(5) = m(6) - m(2)*q;
f(6) = m(6) - m(5)*(.01/.99);

end

I can't seem to figure out how to get rid of this error.

[Ryan]

the error is specifically referring to the " f(4) = -m(5) + m(1) + 2*Ce + Cc*q"

Answer 1

[Walter Roberson]

The variable "q" is not a scalar. Possibly it was not previously initialized.

[Ryan]

why do you say that? from my workspace, it shows that q is a scalar.

[Walter Roberson]

You have the expression

f(4) = -m(5) + m(1) + 2*Ce + Cc*q

m(5) and m(1) and 2 are certain to be scalars or else you would have gotten an error about indexing out of range (if m was empty).So if the expression on the right is producing a non-scalar then Ce or CC or q must be non-scalars, perhaps empty. Ce and CC were used to construct f(1) which did not fail, so they must not be non-scalars. All we are left with as a possibility is q. What does size(q) show ?

dbstop if error

and run the code and check what q is at the time of the error.