I came across the R Programming Wikibook at http://en.wikibooks.org/wiki/R_Programming
It is quite surprisingly good- easy to read for a beginner- handy and concise reference for intermediate users. Some chapters like clustering could do with some more support from the community -see http://en.wikibooks.org/wiki/R_Programming/Clustering
- See packages class, amap and cluster
- See The R bioinformatic page on clustering
But I really liked the pages on Graphics, Modeling and Maths (including Matrix)
I really believe that a consolidated one book online documentation can be achieved for R, only if we follow a moderated-wiki like structure. This can be of a great use- since online help documents for R are currently not concise or present a seemingly professional look (due to multiple formats and styles to the documentation) and they rarely do multiple package comparison. All this has made R books the top selling books on statistics on Amazon but a project like R deserves atleast one comprehensive online and concise book which can be used readily without going through all the scattered multiple documentation- a bit like a R Online Doc.This could help in stage next of the project in getting more users to be comfortable with it.
Any volunteers 🙂 ?