What is the best way to compute trending topics or tags?

Question

Many sites offer some statistics like \"The hottest topics in the last 24h\". For example, Topix.com shows this in its section \"News Trends\". There, you can see the topics

Answer 1

Typically "buzz" is figured out using some form of exponential/log decay mechanism. For an overview of how Hacker News, Reddit, and others handle this in a simple way, see this post.

This doesn't fully address the things that are always popular. What you're looking for seems to be something like Google's "Hot Trends" feature. For that, you could divide the current value by a historical value and then subtract out ones that are below some noise threshold.