Unable to convert expression into double array

Dear all,

In the code I would like to use sym function to calculate the first-order derivative of functions F1- F4 and calculate the values of the derivative in special points. But I keep getting this error:

"Error using symengine Unable to convert expression into double array.

Error in sym/double (line 692)

Xstr = mupadmex('symobj::double', S.s, 0);

t     = 1.1;
phi   = 1.2;
eta_S = 2;
eta_N = eta_S*phi;
sigma = 3;
L_S   = 1000;
H_S   = 500;
L_N   = 800;
H_N   = 1600;
z_N_up = 0.99;
z_S_up = 0.98;

syms z_S z_N p_S p_N w_S_H w_N_L w_N_H

F1  = z_N*log(w_S_H*w_N_L/w_N_H) - [log(w_N_L)-log(t)-sigma*(sigma-1)^(-1)*log(phi)];
F2  = z_S*log(w_S_H*w_N_L/w_N_H) - [log(w_N_L)-log(t)-sigma*(sigma-1)^(-1)*log(phi)];
F3  = p_N^(1-sigma) - eta_S^(sigma)*t^(1-sigma)*[(1-sigma)*log(w_S_H)]^(-1)*[w_S_H^(z_N*(1-sigma))-1] - eta_N^(sigma)*w_N_L^(1-sigma)*[(1-sigma)*log(w_N_H/w_N_L)]^(-1)*[(w_N_H/w_N_L)^(1-sigma)-(w_N_H/w_N_L)^(z_N*(1-sigma))];
F4  = p_S^(1-sigma) - eta_S^(sigma)*[(1-sigma)*log(w_S_H)]^(-1)*[w_S_H^(z_S*(1-sigma))-1] - eta_N^(sigma)*t^(1-sigma)*w_N_L^(1-sigma)*[(1-sigma)*log(w_N_H/w_N_L)]^(-1)*[(w_N_H/w_N_L)^(1-sigma)-(w_N_H/w_N_L)^(z_S*(1-sigma))];

F11 = diff(F1,z_S);
F21 = diff(F2,z_S);
F31 = diff(F3,z_S);
F41 = diff(F4,z_S);

double(F11)
double(F21)
double(F31)
double(F41)

How can I obtain the numerical values of F11, F21,F31 and F41 given special values of z_S z_N p_S p_N w_S_H w_N_L w_N_H?

Answer 1

[Matt J]

One way is to convert the symbolic expression to a function with matlabFunction. Then you can pass values to it as for any function.

[sxj]

Hey, Matt, Thanks for the quick reply. It works

[Matt J]

You're welcome, but please Accept-click the answer to certify that it worked.

Answer 2

[Walter Roberson]

Your F21 and F41 involve several variables including w_N_H. You do not assign values to those variables, so you cannot convert the expression to numeric values.