ddply用于创建列表的并集

Question

我有一个包含customerid和列表的数据框.我想合并那些与同一客户有关的清单.

library(plyr)
subsets <- list(c("a", "d", "e"), c("a", "b", "c", "e"))
customerids <- c(1,1)
transactions <- data.frame(customerid = customerids,subset =I(subsets))
> transactions
  customerid     subset
1          1    a, d, e
2          1 a, b, c, e

如果我想将子集与ddply合并,我会得到一个扩展的结果

> ddply(transactions, .(customerid), summarise, subset=Reduce(union,subset))
  customerid subset
1          1   a
2          1   d
3          1   e
4          1   b
5          1   c

虽然我希望所有的结果都在一排.

Answer 1

你可以这样做：

ddply(transactions, .(customerid), function(x) 
            data.frame(subset=I(list(unlist(x$subset)))))

编辑：我不确定我是否遵循了您的评论。但是，如果您只想在每个customeridfor中使用唯一值subset，那么：

ddply(transactions, .(customerid), function(x) 
            data.frame(subset=I(list(unique(unlist(x$subset))))))