Question

我有一个数据框：

zz <- "id  created  status  snap
ZX1 2012-09-07  A   2013-01-01
ZX1 2012-09-07  B   2013-01-02
ZX1 2012-10-11  B   2013-01-03
ZX1 2012-12-03  B   2013-01-04
ZY2 2014-01-04  A   2013-01-01
ZY2 2014-01-04  A   2013-01-04
ZZ3 2014-08-06  A   2013-01-01
ZZ3 2014-05-06  B   2013-01-03
ZZ3 2014-07-15  C   2013-01-04"

df <- read.table(text=zz, header=T)

我需要为每个id选择并应用最小创建日期。

输出：

id  created status  snap
ZX1 2012-09-07  A   2013-01-01
ZX1 2012-09-07  B   2013-01-02
ZX1 2012-09-07  B   2013-01-03
ZX1 2012-09-07  B   2013-01-04
ZY2 2014-01-04  A   2013-01-01
ZY2 2014-01-04  A   2013-01-04
ZZ3 2014-05-06  A   2013-01-01
ZZ3 2014-05-06  B   2013-01-03
ZZ3 2014-05-06  C   2013-01-04

示例：ZX1＆＃34;已创建＆＃34;所有观察结果应为2012-09-07。

Answer 1

尝试

library(dplyr) 
df %>%
   group_by(id) %>%
   mutate(created=min(as.Date(created)))
#      id    created status       snap
#1 ZX1 2012-09-07      A 2013-01-01
#2 ZX1 2012-09-07      B 2013-01-02
#3 ZX1 2012-09-07      B 2013-01-03
#4 ZX1 2012-09-07      B 2013-01-04
#5 ZY2 2014-01-04      A 2013-01-01
#6 ZY2 2014-01-04      A 2013-01-04
#7 ZZ3 2014-05-06      A 2013-01-01
#8 ZZ3 2014-05-06      B 2013-01-03
#9 ZZ3 2014-05-06      C 2013-01-04

或使用data.table

library(data.table)
setDT(df)[, created1 := min(as.Date(created)), by=id][]

将最小日期应用于一组观察的其余部分

1 个答案: