[R-pkgs] plyr 0.1.9

Hadley Wickham hadley at rice.edu
Tue Jun 23 17:36:41 CEST 2009

plyr is a set of tools for a common set of problems: you need to break
down a big data structure into manageable pieces, operate on each
piece and then put all the pieces back together.  For example, you
might want to:

  * fit the same model to subsets of a data frame
  * quickly calculate summary statistics for each group
  * perform group-wise transformations like scaling or standardising
  * eliminate for-loops in your code

It's already possible to do this with built-in functions (like split
and the apply functions), but plyr just makes it all a bit easier

  * absolutely consistent names, arguments and outputs
  * 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

Some considerable effort has been put into making plyr fast and memory
efficient, and in most cases it is faster than the built-in functions.

You can find out more at http://had.co.nz/plyr/, including a 20 page
introductory guide, http://had.co.nz/plyr/plyr-intro.pdf.  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

plyr 0.1.9 (2009-06-23) ---------------------------------------------------

* fix bug in rbind.fill when NULLs present in list
* improve each to recognise when all elements are numeric
* fix labelling bug in d*ply when .drop = FALSE
* additional methods for quoted objects
* add summarise helper - this function is like transform, but creates
a new data frame rather than reusing the old (thanks to Brendan
O'Connor for the neat idea)


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