R:按ID分组的频率 [英] R: frequency with group by ID
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问题描述
我有一个这样的数据框:
I have a data frame like this:
ID Cont
1 a
1 a
1 b
2 a
2 c
2 d
我需要通过ID报告续"的频率.输出应该是
I need to report the frequence of "Cont" by ID. The output should be
ID Cont Freq
1 a 2
1 b 1
2 a 1
2 c 1
2 d 1
推荐答案
使用dplyr
,您可以同时使用n()
来group_by
ID
和Cont
和summarise
来获取Freq
:
Using dplyr
, you can group_by
both ID
and Cont
and summarise
using n()
to get Freq
:
library(dplyr)
res <- df %>% group_by(ID,Cont) %>% summarise(Freq=n())
##Source: local data frame [5 x 3]
##Groups: ID [?]
##
## ID Cont Freq
## <int> <fctr> <int>
##1 1 a 2
##2 1 b 1
##3 2 a 1
##4 2 c 1
##5 2 d 1
数据:
df <- structure(list(ID = c(1L, 1L, 1L, 2L, 2L, 2L), Cont = structure(c(1L,
1L, 2L, 1L, 3L, 4L), .Label = c("a", "b", "c", "d"), class = "factor")), .Names = c("ID",
"Cont"), class = "data.frame", row.names = c(NA, -6L))
## ID Cont
##1 1 a
##2 1 a
##3 1 b
##4 2 a
##5 2 c
##6 2 d
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