Question

我想计算组均值，但将它们保存为原始数据旁边的向量。有没有一种有效的方法在dplyr中执行此操作？

原始data.frame：

dat <- data.frame(
  group = c("A","A","A","B","B","B"),
  value = c(4, 5, 6, 7, 8, 9)
  )

> dat
  group value
1     A     4
2     A     5
3     A     6
4     B     7
5     B     8
6     B     9

所需的data.frame具有完整的组矢量意味着：

dat2 <- data.frame(
  group = c("A","A","A","B","B","B"),
  value = c(4, 5, 6, 7, 8, 9),
  groupmeanvalue = c(5, 5, 5, 8, 8, 8)
)

> dat2
  group value groupmeanvalue
1     A     4              5
2     A     5              5
3     A     6              5
4     B     7              8
5     B     8              8
6     B     9              8

Answer 1

dat <- dat %>% 
  group_by(group) %>%
  mutate(groupmeanvalue = mean(value))

dat
Source: local data frame [6 x 3]
Groups: group [2]

   group value groupmeanvalue
  (fctr) (dbl)          (dbl)
1      A     4              5
2      A     5              5
3      A     6              5
4      B     7              8
5      B     8              8
6      B     9              8

Answer 2

我们可以使用ave

中的base R

dat$groupmeanvalue <- with(dat, ave(value, group))
dat$groupmeanvalue
#[1] 5 5 5 8 8 8

或data.table

的其他选项

library(data.table)
setDT(dat)[, groupmeanvalue := mean(value), by = group]

意味着作为dplyr中的窗口函数

2 个答案: