October 24, 2011

Split, Apply, Combine: Using Base R (Introduction to Statistical Computing)

Lecture 12: Design patterns and their benefits: clarity on what is to be done, flexibility about how to do it, ease of adapting others' solutions. The split/apply/combine pattern: divide big structured data sets up into smaller, related parts; apply the same analysis to each part independently; combine the results of the analyses. Trivial example: rowSums, colSums. Further examples. Iteration as a verbose, painful and clumsy implementation of split/apply/combine. Tools for split/apply/combine in basic R: the apply function for arrays, lapply for lists, mapply, etc.; split. Detailed example with a complicated data set: Masters 2011 Golf Tournament. R, data.

Introduction to Statistical Computing

Posted by crshalizi at October 24, 2011 13:50 | permanent link

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