Summa is a little CoffeeScript / JavaScript library for descriptive (summary) statistics and working with distributions (PMF, CDF). It got started as some helpers to aid me in solving exercises in Allen Downey's excellent Think Stats book.

Should work both in the browser and in node.js.

Open-source because why-the-heck-not, but don't expect any support. Because I'm working on this library as I learn, it's highly likely that some of the functionality or terminology will be weird or produce wrong results. You've been warned.

If you're looking for something more full-featured, try R, SciPy.stats or any of the commercial statistics packages out there like SAS, SPSS and Stata.