Multiply Even Variables in an Array

I have initialized an array with values.

I have made a function that will determine if the integers within the array are odd or even. For the integers that are even, I want to multiply them by a set, finite number such as 5.

How would I do this?

Answer 1

[Steven Lord]

Hint: use logical indexing twice in the onle line of code that performs this replacement.

[Richard Dillenson]

I don't understand why I cannot do *=10 but I am able to assign them new finite values.

[Steven Lord]

There's no such thing as a *= operator in MATLAB. But you have gotten half the solution:

x(rem(x, 2) == 0) = 

That refers to the even elements in x on the left side. Now you need to figure out how to use logical indexing on the right of the equals sign.

[Richard Dillenson]

I cannot figure this out based upon the link you sent above. Can I get another hint?

[James Tursa]

Just use a variable to store the logical indexes. E.g.,

ix = rem(x,2)==0;

Then use ix for indexing downstream in your code.

[Steven Lord]

You want to take the even numbers from their locations in x, multiply them by 5, then stick the results back in the locations of the even numbers in the original x vector. Your left side does the "then stick the results back in the locations of the even numbers in the original x vector" piece. Given that's what it does, how would you do the "take the even numbers from their locations in x, multiply them by 5" piece?

[Richard Dillenson]

x(rem(x, 2) == 0) = x(rem(x,2)*5;

Thank you so much!

[James Tursa]

This is not correct. You need to use the exact same indexing on both sides of the assignment.

[Steven Lord]

There are also mismatched parentheses. From the fact that Richard Dillenson said "Thank you" I assume that's an error when the solution was copy-and-pasted into Answers not an error in the code they ran.