小编Lil*_*eco的帖子

我有一个像这样的data.frame

x <- data.frame(Category=factor(c("One", "One", "Four", "Two","Two",
"Three", "Two", "Four","Three")),
City=factor(c("D","A","B","B","A","D","A","C","C")),
Frequency=c(10,1,5,2,14,8,20,3,5))

  Category City Frequency
1      One    D        10
2      One    A         1
3     Four    B         5
4      Two    B         2
5      Two    A        14
6    Three    D         8
7      Two    A        20
8     Four    C         3
9    Three    C         5

我想用sum(频率)制作一个数据透视表,并使用ddply函数,如下所示:

ddply(x,.(Category,City),summarize,Total=sum(Frequency))
  Category City Total
1     Four    B     5
2     Four    C     3
3      One    A     1
4      One    D    10
5    Three    C     5
6    Three    D     8 …