[MUSIC] Okay, so that's one way to
retrieve a document of interest. Just take all articles out there,
scan over them, and find the one that's most similar
according to the metric that we define. But another thing we might be interested
in doing is clustering documents that are related, so for example. You might have a whole bunch of
articles about sports or world news or different things like this, and if we
can structure our corpus in this way, if a person is reading
an article that's about sports, then we can very quickly search over
all the other articles about sports, instead of looking at every article
that's out there in the entire corpus. But the challenge here is the fact that
these articles aren't going to have labels. It's not gonna be like the New York Times,
where you go and somebody says,
this is an education article. Okay, and all we have are articles,
and what we like to do, or discover these underlying
groups of articles. Okay, so the goal is to discover these
groups or clusters of related articles, and like I mentioned, one might represent
a set of articles like sports, and another one a set of
articles about world news. For the time being, let's actually assume
that someone provides us with labels, so, somebody goes through and
reads every article or at least a large sub-set of articles
in our corpus and labels them and says, okay, these articles,
these are all about sports. And these ones,
these are about world news. And these about entertainment. And these ones are about science. So we have some set of articles that
have labels associated with them. Well, in this case, when we have
our query article and we like to sign it to a cluster, this ends up being
just a multi-class classification problem. Because the question is just,
here is my query article, I don't know the label associated with it,
and I have a bunch of label document. I have the labels world news, science,
sports, entertainment, technology, and I just wanna classify which
class this article belongs to, okay? So this is the question. It's just a multi class
classification problem. So if that were the case, that would be an
example of a supervise learning problem. [MUSIC]