title: Apriori algorithm Anti-monotonic vs monotonic
body: <p>According to Wikipedia, a <a href="https://en.wikipedia.org/wiki/Monotonic_function" rel="nofollow noreferrer">monotonic function</a> is a function that is either increasing or decreasing. If a function is increasing and decreasing then it's not a monotonic function or it's an <em>anti-monotonic</em> function. </p>
  
  <p>But the data mining book, "Data Mining: Concepts and Techniques," describes <em>anti-monotonic</em> property as: If a set is infrequent then all of its supersets are also infrequent.</p>
  
  <p>Doesn't this property look the same as monotonic according to Wikipedia? What is the difference between the two? </p>