import symjava.symbolic.Expr;

Expr[] params = eq.getParams();

for(int j=0; j<eq.getParams().length; j++) {

Expr df = res[i].diff(params[j]);

J[i][j] = df;

}

System.out.println(J);

System.out.println(res);

package symjava.examples;

import static symjava.symbolic.Symbol.*;

import symjava.matrix.*;

import symjava.symbolic.*;

public class Example4 {

public static void main(String[] args) {

Func u = new Func("u", x,y,z);

Func u0 = new Func("u0", x,y,z);

Func q = new Func("q", x,y,z);

Func q0 = new Func("q0", x,y,z);

Func f = new Func("f", x,y,z);

Func lamd = new Func("\\lambda ", x,y,z);

Expr reg_term = (q-q0)*(q-q0)*0.5*0.1;

Func L = new Func("L",(u-u0)*(u-u0)/2 + reg_term + q*Dot.apply(Grad.apply(u), Grad.apply(lamd)) - f*lamd);

System.out.println("Lagrange L(u, \\lambda, q) = \n"+L);

Func phi = new Func("\\phi ", x,y,z);

Func psi = new Func("\\psi ", x,y,z);

Func chi = new Func("\\chi ", x,y,z);

Expr[] xs = new Expr[]{u, lamd, q };

Expr[] dxs = new Expr[]{phi, psi, chi };

SymVector Lx = Grad.apply(L, xs, dxs);

System.out.println("\nGradient Lx = (Lu, Llamd, Lq) =");

System.out.println(Lx);

Func du = new Func("\\delta{u}", x,y,z);

Func dl = new Func("\\delta{\\lambda}", x,y,z);

Func dq = new Func("\\delta{q}", x,y,z);

Expr[] dxs2 = new Expr[] { du, dl, dq };

SymMatrix Lxx = new SymMatrix();

for(Expr Lxi : Lx) {

Lxx.add(Grad.apply(Lxi, xs, dxs2));

}

System.out.println("\nHessian Matrix =");

System.out.println(Lxx);

}

}