changing expression to function

i have the values for a=[],b=[],reg1=[],reg2=[], i want to change the expr = expr + 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)) into a function.

expr = optimexpr;
for i = 1:numel(a)
    r1 = reg1(i);
    r2 = reg2(i);
    %syms expr x y w 
    disp(expr)
    expr = expr + 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));

is the following method is correct:

    syms expr x y w
    disp(expr)
    ht=matlabFunction(expr);

Also, if I want to perform minimization of the expr = expr + 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)), after changing into a function, please suggest a way

Answer 1

[Dyuman Joshi]

You will have to define x and y as symbolic variables first -

%Random values for example
a = rand(1,10);
b = rand(1,10);

reg1 = randperm(n);
reg2 = randperm(n);
w = randperm(n);

n = numel(a);
syms x y [1 n]
size(x)

ans = 1×2

1 10

size(y)

ans = 1×2

1 10

expr = 0;

for i = 1:numel(a)
    r1 = reg1(i);
    r2 = reg2(i);
    expr = expr + 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

%display the expression
disp(expr)

expr = 

%Convert the expression to a function handle with vector inputs arguments
F = matlabFunction(expr, "Vars", {x, y})

F = function_handle with value:
    @(in1,in2)sqrt((in1(:,2)-8.014959555768938e-1).^2+(in2(:,2)-7.559548740512954e-1).^2).*4.0-sqrt((in1(:,5)-8.014959555768938e-1).^2+(in2(:,5)-7.559548740512954e-1).^2).*3.0+sqrt((in2(:,5)-4.61498021717956e-1).^2+(in1(:,5)-3.474030646560082e-1).^2).*8.0-sqrt((in2(:,9)-4.61498021717956e-1).^2+(in1(:,9)-3.474030646560082e-1).^2).*4.0-sqrt((in2(:,2)-9.29217944804744e-1).^2+(in1(:,2)-2.704418800038694e-1).^2).*7.0+sqrt((in2(:,3)-9.29217944804744e-1).^2+(in1(:,3)-2.704418800038694e-1).^2).*3.0-sqrt((in1(:,3)-4.377482537830102e-2).^2+(in2(:,3)-8.593346111369374e-1).^2).*6.0+sqrt((in1(:,6)-4.377482537830102e-2).^2+(in2(:,6)-8.593346111369374e-1).^2).*7.0+sqrt((in1(:,9)-6.910514959968014e-1).^2+(in2(:,9)-5.800488220855226e-1).^2).*5.0-sqrt((in1(:,10)-6.910514959968014e-1).^2+(in2(:,10)-5.800488220855226e-1).^2).*8.0-sqrt((in2(:,6)-4.29276521870975e-1).^2+(in1(:,6)-3.633048837974125e-1).^2)+sqrt((in2(:,8)-4.29276521870975e-1).^2+(in1(:,8)-3.633048837974125e-1).^2).*6.0-sqrt((in2(:,8)-4.666644464857098e-1).^2+(in1(:,8)-8.109265130783774e-1).^2).*5.0+sqrt((in2(:,10)-4.666644464857098e-1).^2+(in1(:,10)-8.109265130783774e-1).^2)

[Akhil]

when i am modifying the above code as per my requirement:

expr = 0;

for i = 1:numel(a)

r1 = reg1(i);

r2 = reg2(i);

expr = expr + 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

syms x y w [1 26]

size(x);

size(y);

size(w);

% Define the expression as a function handle

expr_func = matlabFunction(expr, 'Vars', {x, y,w});

error is coming which says:Incorrect number or types of inputs or outputs for function 'matlabFunction'.

[Dyuman Joshi]

Do you have the Symbolic Math Toolbox licensed and installed?

Type "ver" and see if you have it installed

ver

-----------------------------------------------------------------------------------------------------
MATLAB Version: 23.2.0.2489961 (R2023b) Update 6
MATLAB License Number: 0
Operating System: Linux 5.4.233-0504233-generic #202302250651 SMP Sat Feb 25 12:26:27 UTC 2023 x86_64
Java Version: Java 1.8.0_292-b10 with AdoptOpenJDK OpenJDK 64-Bit Server VM mixed mode
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errmsg =

  0×0 empty char array

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