Why I cannot get negative answer ?

clear all; close all; clc;
x = input('x= ');
y = input('y= ');

if (x>=5) & (y>2)
    f(x,y)=x^2-y;
elseif (x<5) | (y>0 & y<=2)
    f(x,y) = x-y^2;
else (x<0 & x>0) & (y<0)
    f(x,y)= x^3 + y^3;
end
f(x,y)

%when I try input x =0 and y=2 it does not run
%Index in position 1 is invalid. Array indices must be positive integers or logical values.
%How to I solve that?
%Thank you very much

[VBBV]

clear all; close all; clc;
x = 0 ; 
y = 2 ;

if (x>=5) & (y>2)
    f = @(x,y) x^2-y;  % define function using function handle 
    f(x,y)
elseif (x<5) | (y>0 & y<=2)
    f= @(x,y) x-y^2;
    f(x,y)
else (x<0 & x>0) & (y<0)
    f = @(x,y) x^3 + y^3;
    f(x,y)
end

ans = -4

Define the function using its function handle as the way you try to call function

Answer 1

[Matt J]

x=0; y=2;


if (x>=5) & (y>2)
    f=x^2-y;
elseif (x<5) | (y>0 & y<=2)
    f = x-y^2;
else (x<0 & x>0) & (y<0)
    f= x^3 + y^3;
end
f

f = -4

[Vo]

why we use f due to f(x,y) sir ?

[Matt J]

Because, "array indices must be positive integers or logical values"

For example:

A=rand(1,4)

A = 1×4

0.8551 0.1501 0.7576 0.0665

We can do

A(1)

ans = 0.8551

A(2)

ans = 0.1501

but not,

A(0)

Array indices must be positive integers or logical values.

There is no location in the vector known as A(0).