【3.4】R数据变形--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:
更多阅读:
http://www.cnblogs.com/cloudtj/articles/5540913.html
http://www.jianshu.com/p/bfddfe29aa39
revalue
library(plyr) # For the revalue() function
birthwt1$smoke
ddply
