Optimization problem with multivariable functions

Hey!

I try to optimize a function with syms but get an error. Im new to syms but wanted to try and learn. The code i been written is:

% Testing_syms_functions

clc

D=1; S=1;L=1;q=1;
syms x a1 a2 b2 b3 b4 

ws(x, a1, a2, b2, b3, b4) = a1*x + a2*x^2;
wb(x, a1, a2, b2, b3, b4) = b2*x^2 + b3*x^3 + b4*x^4;

dwsx=diff(ws,x,1);
d2wbx=diff(wb,x,2);

U1 = 0.5*int((D*(d2wbx)^2 + S*(dwsx)^2),0,L) ;
U2 = -int(q*(ws+wb),0,L);

E = U1 + U2;

dEa1=diff(E,a1,1);
dEa2=diff(E,a2,1);
dEb2=diff(E,b2,1);
dEb3=diff(E,b3,1);
dEb4=diff(E,b4,1);

dE=[dEa1 dEa2 dEb2 dEb3 dEb4];

H=[diff(dEa1,a1,1), diff(dEa2,a1,1), diff(dEb2,a1,1), diff(dEb3,a1,1), diff(dEb4,a1,1);
    diff(dEa2,a1,1), diff(dEa2,a2,1) diff(dEb2,a2,1), diff(dEb3,a2,1), diff(dEb4,a2,1);
    diff(dEb2,a1,1), diff(dEb2,a2,1), diff(dEb2,b2,1), diff(dEb2,b3,1),diff(dEb2,b4,1);
    diff(dEb3,a1,1), diff(dEb3,a2,1), diff(dEb3,b2,1), diff(dEb3,b3,1), diff(dEb3,b4,1);
    diff(dEb4,a1,1), diff(dEb4,a2,1), diff(dEb4,b2,1), diff(dEb4,b3,1), diff(dEb4,b4,1);];

c=[2; 1; 1; 1; 1];                         
kmax=10; tol=0.5e-8;                

for k=1:kmax
d=-H\dE(c);
c=c+d;
disp([c' norm(d)])
if norm(d)<tol, break, end
end

Now i get an error saying:

Error using symfun/subsref (line 172)
Symbolic function expected 5 input arguments but received 1.

Error in Testing_syms_functions (line 41)
d=-H\dE(c);

Can someone please help me?

BR

Daniel

[Torsten]

dE must be a column vector, not a row vector.

And to evaluate dE for a numerical input vector c, you will have to use the "subs" command, I guess.

Best wishes

Torsten.