expression to function using syms

Question

Akhil 2024-1-16

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2070676-expression-to-function-using-syms

评论： Akhil 2024-1-17

In the following code, i am trying to learn how to use syms to convert an expression to function. Is the following manner is correct. Also If i want to perform minimization using fminsearch how it can be done. The expression is =w(r2) * sqrt((x(r1)-a(i))^2 + (y(r1)-b(i))^2) - w(r1) * sqrt((x(r2)-a(i))^2 + (y(r2)-b(i))^2)

x=optimvar('x',1,26);
y=optimvar('y',1,26);
w=optimvar('w',1,26);
f = 0;
for i = 1:numel(a)
    r1 = reg1(i);
    r2 = reg2(i);
    f = f + w(r2) * sqrt((x(r1)-a(i))^2 + (y(r1)-b(i))^2) - w(r1) * sqrt((x(r2)-a(i))^2 + (y(r2)-b(i))^2);
end
x0=0;
y0=0;
w0=10;
%function f=ht(x,y,w)
% x=zeros(1,26);
% y=zeros(1,26);
%w=zeros(1,26);
%end
syms x y w [1 26]
%size(x);
%size(y);
%size(w);
expr_func = matlabFunction(f, 'Vars', {f,x, y,w,a,b,r1,r2}); 

also for expr_func = matlabFunction(f, 'Vars', {f,x, y,w,a,b,r1,r2}), error coming out is Incorrect number or types of inputs or outputs for function 'matlabFunction'.

How to rectify this

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Torsten 2024-1-16

Is there any reason why w(i) = 0 and x,y arbitrary (1<=i<=26) does not solve your optimization ? In this case, f will be 0.

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Answer 1

Walter Roberson 2024-1-16

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2070676-expression-to-function-using-syms#answer_1391031

在 MATLAB Online 中打开

Assuming a b reg1 reg2 are known ahead of time:

syms x [1 26]
syms y [1 26]
syms w [1 26]
f = 0;
for i = 1:numel(a)
    r1 = reg1(i);
    r2 = reg2(i);
    f = f + w(r2) * sqrt((x(r1)-a(i))^2 + (y(r1)-b(i))^2) - w(r1) * sqrt((x(r2)-a(i))^2 + (y(r2)-b(i))^2);
end
expr_func = matlabFunction(f, 'Vars', {[x, y, w]}); 