Error using MATLAB fsolve function and not sure why.

Im having trouble with an error using the function fsolve for a system of equations.

f = @(x) [h*(Tinf-T1)+ep*sigma*Ts-ep*sigma*x(2)-x(1); x(1)*(1/rr+1/rc)-(x(2)-Ts); x(1)*r2-(x(3)-x(2)); x(1)*r3(x(4)-x(3))];

x = fsolve(f, [1 1 1 1]);

the error is

Error in Me603HW55 (line 43)

x = fsolve(f, [1 1 1 1]);

Caused by:

Failure in initial objective function evaluation. FSOLVE cannot continue.

Answer 1

[Walter Roberson]

x(1)*r3(x(4)-x(3)

That code tries to index r3 at location x(4)-x(3)

Remember, MATLAB has absolutely no implied multiplication. NAME(EXPRESSION) is always either array indexing or function invocation, and never means multiplication of the content of NAME by the EXPRESSION .