Data Analysis with R, Second Edition - Second Edition

Recycling

The last important property of vectors and vector operations in R is that they can be recycled. To understand what I mean, examine the following expression:

  > our.vect + 3 
  [1] 12  9 10  8  6  3 12 

This expression adds three to each digit in Jenny's phone number. Although it may look so, R is not performing this operation between a vector and a single value. Remember when I said that single values are actually vectors of the length 1? What is really happening here is that R is told to perform element-wise addition on a vector of length 7 and a vector of length 1. As element-wise addition is not defined for vectors of differing lengths, R recycles the smaller vector until it reaches the same length as that of the bigger vector. Once ...