If statement to target certain area of f(i,j)?

Assume I have a function of F(i,j) in grid points,

Am i typing my if statement correctly to target the 2 areas shown above? MATLAB console has not shown any error so far. Thanks in advance.

% Subroutine
function k=X(x,y,dx)
if (x <=5 & y <=2) & (x >= 10 & y >= 10)
    constant = 85;  % beta
else
    constant = 100; % alpha
end
k=constant*dx;
end

Answer 1

[KSSV]

% Subroutine
function k=X(x,y,dx)
if (x <=5 && y <=2) || (x >= 10 && y >= 10)
    constant = 85;  % beta
else
    constant = 100; % alpha
end
k=constant*dx;
end

[Anna Lin]

I'm actually working with arrays, so I've used the single operator instead of double operators.

Is it better to use the OR operator instead of the AND operator ?

I've tried them both and they both yield the same results

if (x <=5 & y <=2) & (x >= 10 & y >= 10)

if (x <=5 & y <=2) | (x >= 10 & y >= 10)

[Steven Lord]

% if (x <=5 & y <=2) & (x >= 10 & y >= 10)

Is the if condition satisfied for x = 3 and y = 1?

x = 3;
y = 1;
condition = (x <=5 & y <=2) & (x >= 10 & y >= 10)

condition = logical
   0

Why is this false when the point is in the left box in your diagram?

inLeftBox = (x <=5 & y <=2)

inLeftBox = logical
   1

inRightBox = (x >= 10 & y >= 10)

inRightBox = logical
   0

The first condition is true but the second is false and:

true & false % false

ans = logical
   0

In fact this if statement's condition cannot be satisfied. Can you think of an x coordinate that is simultaneously less than or equal to 5 and greater than or equal to 10? Or to put it another way, point out a point in your diagram that's in both the beta boxes.

How about the second if statement?

% if (x <=5 & y <=2) | (x >= 10 & y >= 10)
condition2 = (x <=5 & y <=2) | (x >= 10 & y >= 10)

condition2 = logical
   1

true | false

ans = logical
   1

[Anna Lin]

Now I get it, thank you so much!