Problem with minimizing optimization function with multiple variables

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Meaghan
Meaghan 2017-9-10
编辑： John D'Errico 2017-9-10
I'd like to minimize the function "x^2 +5y^2 +4xy-30x-60y+219". When I did it by hand, I got my minimum to be at 0,15, but I'd like to double check.
My total program is:
function b = f(v)
x = v(1);
y = v(2);
b = (x^2 + 5.*y^2 + 4.*x.*y -30.*x - 60.*y + 219);
v = [0,15]; %guess
a = fminsearch(@f,v)
When I ran the program, the program gave me an error that I didn't have enough input arguments. I think I had enough, since similar programs had similar code.

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采纳的回答

Walter Roberson
Walter Roberson 2017-9-10
function a = f_driver
v = [0,15]; %guess
a = fminsearch(@f,v);
function b = f(v)
x = v(1);
y = v(2);
b = (x^2 + 5.*y^2 + 4.*x.*y -30.*x - 60.*y + 219);

更多回答（1 个）

John D'Errico
John D'Errico 2017-9-10
编辑：John D'Errico 2017-9-10
Defining this m-file...
function b = myfun(v)
x = v(1); y = v(2);
b = (x^2 + 5.*y^2 + 4.*x.*y -30.*x - 60.*y + 219);
Now, test it out.
v0 = [0,15];
vfinal = fminsearch(@myfun,v0)
vfinal =
15 -2.9839e-05
Is the solution correct? Of course. We can verify that.
syms x y
fsym = (x^2 + 5.*y^2 + 4.*x.*y -30.*x - 60.*y + 219);
sol = solve(gradient(fsym) == 0,x,y)
sol =
struct with fields:
x: [1×1 sym]
y: [1×1 sym]
sol.x
ans =
15
sol.y
ans =
0
Since you don't show how you tried it out, I cannot know why it gave you that error. My guess is you are still at the novice stage where you think you can use the "run" button on everything. I wish they would just get rid of the run button in the editor.

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