Solve equations by fsolve and with input anonymous function format

Question

zongxian 2020-9-12

回答： Steven Lord 2020-9-12

By the help document of Matlab, the example of fsolve is:

function F = root2d(x)
F(1) = exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);
F(2) = x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5;

fun = @root2d;
x0 = [0,0];
x = fsolve(fun,x0)

But now outer function transfer a anonymous function of fun, like:

fun = @(x,y) [x+y^2-5, 6*x^2+13*y-5]

Start value x0 = [1, 1]

How do I fit fsolve input format?

Answer 1

Steven Lord 2020-9-12

fun = @(x,y) [x+y^2-5, 6*x^2+13*y-5]

Since fsolve requires the function you pass into it to accept one input, a vector, you need an adapter.

g = @(xy) fun(xy(1), xy(2));

This has the interface fsolve requires and calls fun the way it expects to be called.

g([1 2]) % [0 27]
fun(1, 2) % [0 27]