Basic array property question

Can’t believe I got this far without working this out. :wink: Here’s my code:

class screensaver extends MovieClip {
	var vectx;
	var vecty;

That’s the snippet I used to open the class. Inside the class, I use:

function createShape(y) {
	this.vectx[y] = (Math.random() * 5) + 1;
	this.vecty[y] = (Math.random() * 5) + 1;
}

Y being an incremented count from a for() loop somewhere else in the class. Now. Why can’t I access the items of my array? When I try to trace them, they show as undefined. What am I doing wrong here?