在数据框中的组内运行计数

Question

我有一个在线购物平台的订单数据库.

我正在使用的表格如下所示,其中每一行对应一个客户/项目/日期.

OrderHistory <- data.frame(date=c("2015-02-01", "2015-03-01", "2015-04-01", "2015-03-01", "2015-04-01", "2015-05-01", "2015-05-01"), 
            customer=c("A","A","A","B","B","B","B"),
            item=c("Candy", "Coffee", "Coffee", "Candy", "Candy", "Candy", "Coffee" ))

我想得到的是每个成员订购特定物品的次数的运行计数,因此我可以分析哪些物品是由相同的客户重复订购的,哪些物品是一次订购而不是再次订购.

输出看起来像

out <- data.frame(date=c("2015-02-01", "2015-03-01", "2015-04-01", "2015-03-01", "2015-04-01", "2015-05-01", "2015-05-01"), 
              member=c("A","A","A","B","B","B","B"),
              item=c("Candy", "Coffee", "Coffee", "Candy", "Candy", "Candy", "Coffee" ),
              count=c(1,1,2,1,2,3,1))

我想要一个dplyr解决方案,但我愿意接受任何建议!平台上的确切项目在不断变化,因此解决方案必须是动态的才能解决这个问题.

Answer 1

我相信这应该给你你想要的东西

library(dplyr)
OrderHistory %>%
    group_by(customer, item) %>%
    mutate(count = seq(n()))

Source: local data frame [7 x 4]
Groups: customer, item

        date customer   item count
1 2015-02-01        A  Candy     1
2 2015-03-01        A Coffee     1
3 2015-04-01        A Coffee     2
4 2015-03-01        B  Candy     1
5 2015-04-01        B  Candy     2
6 2015-05-01        B  Candy     3
7 2015-05-01        B Coffee     1