找到日期差异

Question

我有以下数据:

ID GROUP     DATE 
A   GR1   12/01/2013
A   GR1   09/04/2014
A   GR1   01/03/2015
A   GR2   04/04/2015
A   GR2   08/21/2015
A   GR1   01/05/2016
A   GR1   06/28/2016
B   GR2   11/01/2013
B   GR2   06/04/2014
B   GR2   04/15/2015
B   GR3   11/04/2015
B   GR2   03/21/2016
B   GR2   07/05/2016
B   GR1   06/28/2016
C   GR2   01/16/2014
C   GR2   06/04/2014
C   GR2   04/15/2015
C   GR3   11/04/2015
C   GR2   03/21/2016
C   GR2   06/05/2016
C   GR1   06/28/2016

我希望每个小组中的人保持不同.所以新表将如下所示:

ID GROUP     DATE      Diff
A   GR1   12/01/2013
A   GR1   09/04/2014
A   GR1   01/03/2015    398
A   GR2   04/04/2015
A   GR2   08/21/2015    139
A   GR1   01/05/2016
A   GR1   06/28/2016    175
B   GR2   11/01/2013
B   GR2   06/04/2014
B   GR2   04/15/2015    530
B   GR3   11/04/2015
B   GR2   03/21/2016
B   GR2   07/05/2016    106
B   GR1   06/28/2016
C   GR2   01/16/2014
C   GR2   06/04/2014    
C   GR2   04/15/2015    454
C   GR3   11/04/2015
C   GR2   03/21/2016
C   GR2   01/05/2016    76
C   GR1   06/28/2016

"Diff"398栏中的值即将采用差异'01/03/2015' - '12/1/2013'.同样所有其他差异.

现在我的问题是如何获得这种差异？我不能在每个组中取max(date)-min(date),因为group在不同的时间段重复.同样,我不能像SAS那样采用第一个点和最后一个点.

如果有人帮我解决这个问题,我将非常感激.我更喜欢SAS中的解决方案,因为数据量非常大.因此不会留在记忆中.

问候,

Answer 1

library(dplyr)
library(data.table)
df$xxx = rleidv(df[, c("ID","GROUP"),with = FALSE ])
df$DATE = as.Date(df$DATE, format = "%m/%d/%Y")
df %>% group_by(xxx) %>% mutate(diff = max(DATE) - min(DATE)) %>%
       ungroup(xxx) %>% mutate(xxx = NULL)
#     ID GROUP       DATE     diff
#   <chr> <chr>     <date>   <time>
#1      A   GR1 2013-12-01 398 days
#2      A   GR1 2014-09-04 398 days
#3      A   GR1 2015-01-03 398 days
#4      A   GR2 2015-04-04 139 days
#5      A   GR2 2015-08-21 139 days
#6      A   GR1 2016-01-05 175 days
#7      A   GR1 2016-06-28 175 days
#8      B   GR2 2013-11-01 530 days
#9      B   GR2 2014-06-04 530 days
#10     B   GR2 2015-04-15 530 days

仅使用data.table:

library(data.table)
df[, diff := max(DATE)-min(DATE),by = c("xxx")][,xxx:=NULL]

Answer 2

使用SAS做这件事是微不足道的.使用RETAIN保持组的第一个记录的开始日期.您的数据未显示排序,因此要么先排序,要么保留当前顺序(并且组内的记录已按日期排序),那么您可以NOTSORTED在BY语句中使用该选项.

data want ;
  set have ;
  by id group notsorted;
  if first.group then start = date ;
  else if last.group then diff = date - start ;
  retain start;
  drop start;
run;

如果您需要保留当前订单,但日期未在组内排序,那么要发现组中的最小和最大日期,您需要添加另一个变量和更多逻辑.

data want ;
  set have ;
  by id group notsorted;
  if first.group then start = date ;
  if first.group then stop = date ;
  start = min(start,date);
  stop = max(stop,date);
  if last.group and not first.group then diff = stop - start ;
  retain start stop;
  drop start stop;
run;