[R-pkgs] plyr version 1.6

From: Hadley Wickham <hadley_at_rice.edu>
Date: Sat, 30 Jul 2011 08:32:39 -0500

# plyr

plyr is a set of tools for a common set of problems: you need to __split__ up a big data structure into homogeneous pieces, __apply__ a function to each piece and then __combine__ all the results back together. For example, you might want to:

• fit the same model each patient subsets of a data frame
• quickly calculate summary statistics for each group
• perform group-wise transformations like scaling or standardising

It's already possible to do this with base R functions (like split and the apply family of functions), but plyr makes it all a bit easier with:

• totally consistent names, arguments and outputs
• convenient parallelisation through the foreach package
• input from and output to data.frames, matrices and lists
• progress bars to keep track of long running operations
• built-in error recovery, and informative error messages
• labels that are maintained across all transformations

Considerable effort has been put into making plyr fast and memory efficient, and in many cases plyr is as fast as, or faster than, the built-in equivalents.

A detailed introduction to plyr has been published in JSS: "The Split-Apply-Combine Strategy for Data Analysis",

http://www.jstatsoft.org/v40/i01/. You can find out more at
http://had.co.nz/plyr/, or track development at
http://github.com/hadley/plyr. You can ask questions about plyr (and

data manipulation in general) on the plyr mailing list. Sign up at http://groups.google.com/group/manipulatr.

Version 1.6

---

• documentation improved using new features of `roxygen2`
• fixed namespacing issue which lead to lost labels when subsetting the results of `*lply`
• `colwise` automatically strips off split variables.
• `rlply` now correctly deals with `rlply(4, NULL)` (thanks to bug report from Eric Goldlust)
• `rbind.fill` tries harder to keep attributes, retaining the attributes from the first occurrence of each column it finds. It also now works with variables of class `POSIXlt` and preserves the ordered status of factors.
• `arrange` now works with one column data frames

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

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Received on Sat 30 Jul 2011 - 23:35:20 EST