R packages I wish I'd known about earlier

For some reason, I find it harder to find what I'm looking for in the R help than just about any other language. That's why you end up not knowing about useful packages for a very long time. Is that just me?

This article should really just be called "Everyone should just follow Hadley's Github". Actually, someone should write that.

If you want to do any sort of stock analysis, quantmod is really great as it bundles a number of other related packages with financial application together: <a href="http://www.quantmod.com/" rel="nofollow">http://www.quantmod.com/</a>.<p>If you have to deal with directed graphs, iGraph <a href="http://igraph.sourceforge.net/" rel="nofollow">http://igraph.sourceforge.net/</a>.<p><i>Related Blog Posts</i><p><a href="http://www.r-chart.com/2010/06/stock-analysis-using-r.html" rel="nofollow">http://www.r-chart.com/2010/06/stock-analysis-using-r.html</a><p><a href="http://www.r-chart.com/2010/06/analyze-twitter-data-using-r.html" rel="nofollow">http://www.r-chart.com/2010/06/analyze-twitter-data-using-r....</a>

ddply can be very slow. Strongly recommended to get your data into the form you want in something map-reduce-y _then_ throw it into R for analysis and graphing.

data.table deserves a mention here too. It simplifies and speeds up dataframe operations<p>see ?data.table

Caret (<a href="http://caret.r-forge.r-project.org/" rel="nofollow">http://caret.r-forge.r-project.org/</a>) is another package that should make the list, if you are using machine learning packages in R.<p>Caret gives you a common interface to you use a huge list of classifiers. Plus, it has some nice functions for data preparation.

The list of database connectors should also include RSQLite:<p><a href="http://cran.r-project.org/web/packages/RSQLite/index.html" rel="nofollow">http://cran.r-project.org/web/packages/RSQLite/index.html</a><p>A really useful article though. I'm going to investigate RandomForest.

If only all such lists could include example code and visualizations, very nicely done. Thanks!