检查日期是否相同

Question

我正在尝试编写一段代码来检查列中的日期是否相同。该行将按ID分组，因此，如果组中的任何日期与ID不同，则会对其进行标记。

这是我的数据帧(代码)：

df <- structure(list(ID = c("P40", "P40", "P40", "P40", "P42", "P42"),
                     Date = dmy(c(26072013, 26072013, 2092012, 23082012, 01072014, 01072014))),
                class = "data.frame", row.names = c(NA, -6L))

表格形式：

ID       Date
P40     2013-07-26
P40     2013-07-26
P40     2012-09-24
P40     2012-08-23
P42     2014-07-01
P42     2014-07-01 

这就是我想要实现的：

ID    Contsistent
P40      No
P42      Yes

Answer 1

一种选择是

library(dplyr)
df %>%
    group_by(ID) %>% 
    summarise(Consistent = factor(n_distinct(Date) == 1, 
            levels = c(FALSE, TRUE), labels = c("No", "Yes")))
# A tibble: 2 x 2
#  ID    Consistent
#  <chr> <fct>     
#1 P40   No        
#2 P42   Yes      

或使用data.table

library(data.table)
setDT(df)[, .(Consistent = uniqueN(Date) == 1), .(ID)]
#   ID Consistent
#1: P40      FALSE
#2: P42       TRUE

Answer 2

也许：

library(dplyr)

df %>%
  group_by(ID) %>%
  summarise(Consistent = c("No", "Yes")[(n_distinct(Date) == 1) + 1])

输出：

# A tibble: 2 x 2
  ID    Consistent
  <chr> <chr>     
1 P40   No        
2 P42   Yes     

Answer 3

我们可以使用R base中的聚合来完成此操作

# Check Date for each ID in df
aggregate(Date ~ ID, data= df, function(ID_i){ 
# if there is only one unique Date value in ID_i then the function gives "Yes", otherwise it gives a "No"
          ifelse(length(unique(ID_i)) == 1, "Yes", "No")})

   ID Date
1 P40 No
2 P42 Yes