汇总每天的data.frame

Question

我有一个dat关于汽车销售(Buy=0在数据框中)和购买Buy=1二手车销售商(在数据框中)的数据框架.

  Date       Buy   Price
29-06-2015    1    5000
29-06-2015    0    8000
29-06-2015    1    10000
30-06-2015    0    3500
30-06-2015    0    12000 
...          ...  ...

我需要的是一个新的,汇总的data.frame,它给我每天的购买数量和销售数量,以及当天所有购买和销售的总价格:

  Date      Buys   Sells   Price_Buys  Price_Sells
29-06-2015    2    1         15000        8000
30-06-2015    0    2           0          15500
...          ...  ...

我试着用aggregate(dat$Buy, by=list(Date=dat$Date, FUN=sum)).但是,我仍然在努力如何汇总销售.

Answer 1

这可以非常干净地完成dplyr,按日期分组使用group_by,然后总结summarize:

library(dplyr)
(out <- dat %>%
  group_by(Date) %>%
  summarize(Buys=sum(Buy == 1), Sells=sum(Buy == 0),
            Price_Buys=sum(Price[Buy == 1]), Price_Sells=sum(Price[Buy == 0])))
#         Date  Buys Sells Price_Buys Price_Sells
#       (fctr) (int) (int)      (int)       (int)
# 1 29-06-2015     2     1      15000        8000
# 2 30-06-2015     0     2          0       15500

您现在可以像处理普通数据框一样操纵此对象,例如:

out$newvar <- with(out, Sells*Price_Sells - Buys*Price_Buys)
out
# Source: local data frame [2 x 6]
#         Date  Buys Sells Price_Buys Price_Sells newvar
#       (fctr) (int) (int)      (int)       (int)  (int)
# 1 29-06-2015     2     1      15000        8000 -22000
# 2 30-06-2015     0     2          0       15500  31000