A, coming along this way, and we have another user, B, coming along this way.
Right, so, if user A liked movie one, we would give it a positive rating which
means that we're going to extend positive this way, didn't like it, we would give a
negative rating, 'kay. Similarly, if user B liked movie one, we
would go up positive and if he didn't like movie two, we'd go negative.
And then we define these different points one for each movie one and two, so we
could have movie three, four, five and so on and then each of the dimensions in the
graph are a different user, so its a given idea, okay.
So now these values here have, are some indication of the rating that the user
gave the values, okay. And we'll talk exactly what it is in a
second. but the idea here is, we want to compare
these two lines and see how close they are to one another.
Okay? Because if they're really close, like in
this case right here, that we've drawn, they are really close.
Right? So, user A liked movie one so he rated it
positive. User A also liked movie two, so he rated
that positive. User B liked movie one, so he rated that
positive. And user B also liked movie two, so he
rated that granted more positive. But it is the same.
The vectors for movies one, and movies two are both positive wherein they're
both close to one another. So when we look at the angle between the
vectors, this angle right here is small because they're pointing in the same
direction. What that means is that the users tend to
respond the same to those movies because they're pointing in the same direction.
Similarly if we had the angles like this. It would be the same idea.
What all this is saying is that one user responded negatively to both movies but,
still the same, idea applies that if a user responds negatively to one movie
it's going to respond negatively to the other.
And so on. It's just saying the movies are similar
in taste . Now, here's another example.
Okay we're just moving now. We're keeping movie one over here and
we're moving movie two over here. 'Kay.
So now User A had a positive response to movie one, negative response to movie
two. User B had a positive response to movie
one, and also a positive response to movie two.
Now this angle's getting a little larger here, and you can see.
So now, there is not any same directionality here because the, the
users responded differently, okay. So, user one liked this movie, didn't
like this movie, user two likes this movie and likes this movie.
So, for user two there seemed to have been a positive correlation on his view
taste, but for user one seem to have been negative correlation.
So, right here there is really no correlation at all.