Algorithm To Implement A Word Cloud Like Wordle


Answer :

I'm the creator of Wordle. Here's how Wordle actually works:

Count the words, throw away boring words, and sort by the count, descending. Keep the top N words for some N. Assign each word a font size proportional to its count. Generate a Java2D Shape for each word, using the Java2D API.

Each word "wants" to be somewhere, such as "at some random x position in the vertical center". In decreasing order of frequency, do this for each word:

place the word where it wants to be while it intersects any of the previously placed words     move it one step along an ever-increasing spiral

That's it. The hard part is in doing the intersection-testing efficiently, for which I use last-hit caching, hierarchical bounding boxes, and a quadtree spatial index (all of which are things you can learn more about with some diligent googling).

Edit: As Reto Aebersold pointed out, there's now a book chapter, freely available, that covers this same territory: Beautiful Visualization, Chapter 3: Wordle


Here's a really nice javascript one from Jason Davies that uses d3. You can even use webfonts with it.

Demo: http://www.jasondavies.com/wordcloud/

Github: https://github.com/jasondavies/d3-cloud


I've implemented an algorithm as described by Jonathan Feinberg using python to create a tag cloud. It is far away from the beautiful clouds of wordle.net but it gives you an idea how it could be done.

You can find the project here.


Comments

Post a Comment

Popular posts from this blog

Are Regular VACUUM ANALYZE Still Recommended Under 9.1?

Answer : VACUUM is only needed on updated or deleted rows in non-temporary tables. Obviously you're doing lots of INSERTs but it's not obvious from the description that you're also doing lots of UPDATEs or DELETEs. These operations can be tracked with the pg_stat_all_tables view, specifically the n_tup_upd and n_tup_del columns. Also, even more to the point, there is a n_dead_tup column that tells, per table, how much rows need to be vacuumed. (see Monitoring statistics in the doc for functions and views related to statistics gathering). A possible strategy in your case would be to suppress the scheduled VACUUM, keeping an eye on this view and checking on which tables the n_dead_tup is going up significantly. Then apply the aggressive VACUUM to these tables only. This will be a win if there are large tables whose rows never get deleted nor updated and the aggressive VACUUM is really necessary only on smaller tables. But keep running the ANALYZE for the optimiz
Read more

Can Feynman Diagrams Be Used To Represent Any Perturbation Theory?

Answer : Diagram machinery works also for perturbation theory in classical statistical mechanics and classical field theories. Generally, various kinds of diagrams constitute a pictorial way of talking about tensor products and their contractions while hiding the multi-linear algebra from the layman. In the simplest case, vertices (or blobs) represent vectors, matrices, tensors; vertices have ingoing and/or outgoing ports; ingoing ports denote (contravariant) ro indices; outgoing ports denote (covariant) co indices; directed arcs between blobs give a pair of equal indices summed over; different base spaces ⇔ \Leftrightarrow ⇔ different arc types; symmetric tensors ⇔ \Leftrightarrow ⇔ undirected diagrams; no labels are needed for internal lines. In many cases, the directed arcs are decorated (as thin, thick, broken,wavy, curly lines), each decoration indicating the presence of a so-called propagator, a function of its label to use as a weight in the sum, which may beco
Read more