So what we want to do is how much of this, how much of the total variation y is described by the variation in x? So maybe we can think of it this way, so our denominator, we want what percentage of the total variation in y? So let me write it this way. Let me call this as the squared error from the average. Let me call this, this is equal to the squared error, maybe I'll call this the squared error from the mean of y. And this is really the total variation in y. So let's put that as the denominator.