Question about calling user defined function to another script

hello

first here is my user_defined_function code.(name is A_execute1.m)

function A=A_execute1(r)
global V;
A=pi*r*(sqrt(r^2+((9*V^2)/(pi^2*r^4))));
end

second, this is the script file(i made) that i want to call A_execute1 file to.

(to draw graph to see)

r=[-100:0.01:100];
V=10;
fminbnd('A_execute1',-100, 100)
plot(r,A_execute1(r)), xlabel('r'), ylabel('A')
grid

but it says error that

Error using fminbnd (line 237)

User supplied objective function must return a scalar

value.

Error in test4 (line 3)

fminbnd('A_execute1',-100, 100)

why it says that error?

i think i designed scalar value, not vector.

[Stephen23]

Do not use global variablesto pass parameter values, use the methods shown here: https://www.mathworks.com/help/matlab/math/parameterizing-functions.html

Answer 1

[Matt J]

It returns empty.

%r=[-100:0.01:100];
V=10;

A_execute1(-100)

ans =

     []

Don't use global variables. Use anonymous functions, or other alternatives discussed here.

[r,fval]=fminbnd(@(r) A_execute2(r,V),-100,100)

r = -99.9999

fval = -3.1416e+04

function A=A_execute1(r)
global V;
A=pi*r*(sqrt(r^2+((9*V^2)/(pi^2*r^4))));
end

function A=A_execute2(r,V)
A=pi*r*(sqrt(r^2+((9*V^2)/(pi^2*r^4))));
end

[Matt J]

It really doesn't even make sense to create a separate mfile for such a short function:

V=10;
fun=@(r) pi*r*(sqrt(r^2+((9*V^2)/(pi^2*r^4))));

[r,fval]=fminbnd(fun, -100,100)

r = -99.9999

fval = -3.1416e+04

[N/A]

@Matt J

thx for your answer.

can i draw graph through anonymous function?

plot(@(r)), xlabel(''), ylabel('')
grid

or

plot(fun), xlabel(''), ylabel('')
grid

[Matt J]

Yes, using fplot,

fun=@(r) r.^2;

fplot(fun, [-1,1])

or with,

r=linspace(-1,1);
plot(r,fun(r))