我想在后面加上一个条件项~
in a case_when
功能。
我的例子:
df:
df <- structure(list(x = c("a", "a", "a", "b", "b", "b", "c", "c",
"c", "a", "a", "a"), y = 1:12), class = "data.frame", row.names = c(NA,
-12L))
不起作用的代码:
library(dplyr)
df %>%
group_by(x) %>%
mutate(y = case_when(x=="b" ~ cumsum(y),
TRUE ~ y)) %>%
mutate(y = case_when(x=="a" ~ "what I want: last value of group "b" in column y",
TRUE ~ y))
用言语来说:
-
group_by
x
- 计算
cumsum
对于团体b
在列中y
- 取该组 (=b) 的最后一个值 (=15) 并
- 将此值 (=15) 放入列
y
组在哪里a
期望的输出:
x y
<chr> <dbl>
1 a 15
2 a 15
3 a 15
4 b 4
5 b 9
6 b 15
7 c 7
8 c 8
9 c 9
10 a 15
11 a 15
12 a 15
非常感谢!!!