Nat. Methods 10, 228–238 (2013); published online 10 February 2013; corrected after print 1 April 2013

In the version of this article initially published, the affiliations or names of of the following authors were not correctly communicated to the journal: Nicolas Guex, Heikki Huttunen, Tobias R. Kollman, Tapio Manninen, Matti Nykter, Pekka Ruusuvuori and Michael Seifert. The errors have been corrected in the HTML and PDF versions of the article.