How do I write a code that keeps all the even numbers in a vector and deletes all the odd numbers?

I'm wrote a function in which the input is a single number (n), and every number before that all the way down to 1 is multiplied together. (a factorial) How do I change this so that it only multiplies the even numbers between 1 and n?

Code so far:

product = 1;

arrayIndex = [1:1:n];

for i =1:length(arrayIndex)

    product = product*arrayIndex(i);

end

disp(product);

Really all I want to know is how to check every number in a vector if it is even.

Answer 1

[Nicolas Schmit]

This is how you test if an integer is even.

isEven = @(x) mod(x, 2) == 0
isEven(1)
isEven(2)