title: What does cl parameter in knn function in R mean?
body: <p>I'm using R to implement knn. The knn function in 'class' package contains a parameter called cl:</p>
  
  <pre><code>knn(train, test, cl, k = 1, l = 0, prob = FALSE, use.all = TRUE)
  </code></pre>
  
  <p>It is written in the package documentation that cl is a factor of true classiﬁcations of training set. I don't know that means! could any one help?</p>