Find the minimum of a multi-variable function

Question

emonhossain roy 2019-6-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468476-find-the-minimum-of-a-multi-variable-function

编辑： infinity 2019-6-23

采纳的回答： infinity

Question: Find the minimum of

in the window [0,2]×[2,4] with increment 0.01 for x and y.

My approach:

syms fun(x,y) fx(x,y) fy(x,y) fxy(x,y) x y

=

;

pt=solve([

==0,

==0],[x y]) But it gives me an error.

besides what about the window and increment mentioned that question. Any solution will be appreciated .

Thanks in advance .

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infinity 2019-6-23

Hello,

Could you provide your code and show us what is the error?

emonhossain roy 2019-6-23

code:

clc

clear all

syms fun(x,y) fx(x,y) fy(x,y) fxy(x,y) x y

fun(x,y)=x^2+y^2-2*x-6*y+14;

fx(x,y)=diff(fun(x,y),x);

fy(x,y)=diff(fun(x,y),y);

fxy(x,y)=diff(fx(x,y),y);

pt=solve([fx(x,y)==0,fy(x,y)==0],[x y])

error:

Warning: 4 equations in 2 variables.

> In C:\Program Files\MATLAB\R2013a\toolbox\symbolic\symbolic\symengine.p>symengine at 56

In mupadengine.mupadengine>mupadengine.evalin at 97

In mupadengine.mupadengine>mupadengine.feval at 150

In solve at 170

Warning: Explicit solution could not be found.

> In solve at 179

pt =

[ empty sym ]

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Answer 1

infinity 2019-6-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/468476-find-the-minimum-of-a-multi-variable-function#answer_380423

编辑：infinity 2019-6-23

在 MATLAB Online 中打开

Hello,

In your code, it was not good to put the name like "fun(x,y)". Also, we do not need to declare "fx, fun, fy,.." as symbolic variable. Here is a small code that you can refer

clear 
syms x y
fun=x^2+y^2-2*x-6*y+14;
fx=diff(fun,x);
fy=diff(fun,y);
pt=solve([fx==0,fy==0],[x y]);
% pt=solve(fx==0,fy==0);
sol = struct2array(pt)