Chapter 12. Data Reshaping
As noted in Chapter 11, manipulating the data takes a great deal of effort before serious analysis can begin. In this chapter we will consider when the data needs to be rearranged from column oriented to row oriented (or the opposite) and when the data are in multiple, separate sets and need to be combined into one.
There are base functions to accomplish these tasks but we will focus on those in plyr, reshape2 and data.table.
12.1. cbind and rbind
The simplest case is when we have two datasets with either identical columns (both the number of and names) or the same number of rows. In this case, either rbind or cbind work great.
As a first trivial example, we create two simple data.frames by combining a few vector ...
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