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Whats mistake in this code....can anybody guide me?
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z = sym('2*x1 * x1 + x2*x2 + 3*x3*x3');
syms x1 x2 x3 a;
gradz = [diff(z,x1); diff(z,x2); diff(z,x3)];
x1(1)=2;
x2(1)=-2;
x3(1)=1;
for k=2:5
p=subs(gradz, [x1 x2 x3], [x1(k-1) x2(k-1) x3(k-1)]);
x1a=x1(k-1)+p(1)*a;
x2a=x2(k-1)+p(1)*a;
x3a=x3(k-1)+p(1)*a;
za=subs(z, [x1 x2 x3], [x1a x2a x3a]);
w=solve(za);
x1(k)=x1(k-1)+p(1)*w;
x2(k)=x2(k-1)+p(2)*w;
x3(k)=x3(k-1)+p(3)*w;
end
Its giving error
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回答(1 个)
Walter Roberson
2013-3-24
When the explicit solution could not be found, solve() is returning the empty matrix, which you assign into "w". The empty matrix multiplied by p(1) gives the empty matrix. Add x1(k-1) to the empty matrix and you get the empty matrix. You then try to assign that empty matrix, which is of size 0, to x1(k) which is of size 1.
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