fsolve help

 I would like to use fsolve for two nonlinear equations. When I put explicit equations in a function (LBBnlenew2.m) it is ok. But I need to put each equation as a funtion itself (defined already, with the same variables). In this case the error is:
??? Undefined function or method 'norm' for input arguments of type 'sym'.

Error in ==> trustnleqn at 138 normgradinf = norm(grad,inf);

Error in ==> fsolve at 295 [x,FVAL,JACOB,EXITFLAG,OUTPUT,msg]=...

Error in ==> LBB_Instability_Load_M2_solver2 at 2 x=fsolve('LBBnlenew2',x0);

Please let me know how to avoid the error. Thanks Vasile

Answer 1

[Sean de Wolski]

class(grad)
class(inf)

If either of those are symbolic, you cannot use fsolve() since it's a numeric solver. Look into solve() instead.

[Walter Roberson]

It might be practical in your situation to use matlabFunction() to convert the symbolic function in to a function handle of a MATLAB function.

[Sean de Wolski]

@Walter, good idea, that would make gradObj much easier to use.