Meaning of the if statement

1 view (last 30 days)
function z = in_prod(x,y)
if size(x,2)==size(y,1)
z=x*y
else
z = "The inner dimensions are " + size(x,2) + " and " + size(y,1) + ". Matrix multiplication is not possible";
end
• Can anyone explain me the meaning of this if statement please?
• More specifically, why size(x,2) and size(y,1)? Why not size(x,any other value)?
TIA!
Stephen Cobeldick on 19 Apr 2021
"More specifically, why size(x,2) and size(y,1)?"
Because matrix multiplication is only defined when those dimensions are equal:
"Why not size(x,any other value)?"
Because matrix multiplication is only defined for 2D matrices.

David Fletcher on 19 Apr 2021
Edited: David Fletcher on 19 Apr 2021
The if statement is checking that the number of columns in x (the number two in the argument of size is specifying that the function returns the number of columns) matches the number of rows in y (the number one in the argument of size is specifying that the function returns the number of rows). This ensures that matrix multiplication can be applied to x and y. If the inner dimensions do not match, the matrices cannot be multiplied.
Muhtasim Haque Nahian on 9 May 2021
Thanks for the explanation! It helped