Question

我有一个数据框，它有三列employeeid，开始日期（ydm）和结束日期（ydm）。我的目标是创建另一个包含两列的数据框，一列是员工ID，另一列是日期。第二个数据框将围绕第一个数据框构建，这样它将从第一个数据框获取ID，并且列日期将占用该员工的开始日期和结束日期之间的所有月份。简而言之，我将根据员工的开始日期和结束日期按月将第一个数据框中的数据扩展。

我实际上使用for循环成功创建了代码。问题是，它非常慢，在某些地方我读到它是为了避免r中的循环。有没有一种方法可以更快地完成相同的工作？

下面是我的数据框和代码的示例：

# Creating Data frame
    a<- data.frame(employeeid =c('a','b','c'), StartDate= c('2018-1-1','2018-1-5','2018-11-2'),
                   EndDate= c('2018-1-3','2018-1-9','2018-1-8'), stringsAsFactors = F)
    a$StartDate <- ydm(a$StartDate)
    a$EndDate <- ydm(a$EndDate)

    #second empty data frame
    a1 <-a
    a1 <- a1[0,1:2]

    #my code starts
    r <- 1
    r.1 <- 1
    for (id in a$employeeid) {

      #r.1 <- 1
      for ( i  in format(seq(a[r,2],a[r,3],by="month"), "%Y-%m-%d") ) { 
        a1[r.1,1] <- a[r,1]
        a1[r.1,2] <- i
        r.1 <- r.1 +1  
      } 
      r <- r+1
    }

结果是这样：

我想要相同的结果，但是要快一点

Answer 1

几乎是tidyverse的单行代码：

> result
# A tibble: 12 x 2
   employeeid date      
   <chr>      <date>    
 1 a          2018-01-01
 2 a          2018-02-01
 3 a          2018-03-01
 4 b          2018-05-01
 5 b          2018-06-01
 6 b          2018-07-01
 7 b          2018-08-01
 8 b          2018-09-01
 9 c          2018-11-01
10 c          2018-12-01
11 c          2019-01-01
12 c          2019-02-01

代码

result <- df %>%
    group_by(employeeid) %>%
    summarise(date = list(seq(StartDate,
                              EndDate,
                              by = "month"))) %>%
    unnest()

数据

library(tidyverse)
library(lubridate)
df <- data.frame(employeeid = c('a', 'b', 'c'), 
                 StartDate = ymd(c('2018-1-1', '2018-5-1', '2018-11-1')),
                 EndDate = ymd(c('2018-3-1', '2018-9-1', '2019-02-1')),
                 stringsAsFactors = FALSE)

Answer 2

我会尝试通过应用Apply和一个自定义函数来解决此问题，该函数计算结束和开始的差异。

不确定所需的输出是什么样子，但是在以下示例的功能中，开始和结束之间的所有月份都粘贴在字符串中。

library(lubridate)

# Creating Data frame
a<- data.frame(employeeid =c('a','b','c'), StartDate= c('2018-1-1','2018-1-5','2018-11-2'),
               EndDate= c('2018-2-3','2019-1-9','2020-1-8'), stringsAsFactors = F)
a$StartDate <- ymd(a$StartDate)
a$EndDate <- ymd(a$EndDate)

# create month-name month nummeric value mapping
month_names = month.abb[1:12]


month_dif = function(dates) # function to calc the dif. it expects a 2 units vector to be passed over
{
  start = dates[1] # first unit of the vector is expected to be the start date
  end = dates[2] # second unit is expected to be the end date

  start_month = month(start)
  end_month = month(end) 
  start_year = year(start) 
  end_year = year(end)
  year_dif = end_year - start_year

  if(year_dif == 0){ #if start and end both are in the same year month is start till end
    return(paste(month_names[start_month:end_month], collapse= ", " ))
  } else { #if there is an overlap, mont is start till dezember and jan till end (with x full year in between)
          paste(c(month_names[start_month:12],
          rep(month_names, year_dif-1),
          month_names[1:end_month]), collapse = ", ")
  }
}

apply(a[2:3], 1, month_dif)

输出：

> apply(a[2:3], 1, month_dif)
[1] "Jan, Feb"                                                                 
[2] "Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec, Jan"          
[3] "Nov, Dec, Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec, Jan"

Answer 3

您可以结合使用apply和do.call：

out_apply_list <- apply(X=a, MARGIN=1,
                    FUN=function(x) {
                      data.frame(id= x[1], 
                                 date=seq(from = as.Date(x[2], "%Y-%d-%m"), 
                                          to = as.Date(x[3], "%Y-%d-%m"), 
                                          by = "month"),
                                 row.names = NULL) 
})

df <- do.call(what = rbind, args = out_apply_list)

为您提供以下输出：

> df
   id       date
1   a 2018-01-01
2   a 2018-02-01
3   a 2018-03-01
4   b 2018-05-01
5   b 2018-06-01
6   b 2018-07-01
7   b 2018-08-01
8   b 2018-09-01
9   c 2018-02-11
10  c 2018-03-11
11  c 2018-04-11
12  c 2018-05-11
13  c 2018-06-11
14  c 2018-07-11

Answer 4

为了完整起见，这里用data.table简洁地一行：

library(data.table)
setDT(a)[, .(StartDate = seq(StartDate, EndDate, by = "month")), by = employeeid]

    employeeid  StartDate
 1:          a 2018-01-01
 2:          a 2018-02-01
 3:          a 2018-03-01
 4:          b 2018-05-01
 5:          b 2018-06-01
 6:          b 2018-07-01
 7:          b 2018-08-01
 8:          b 2018-09-01
 9:          c 2018-02-11
10:          c 2018-03-11
11:          c 2018-04-11
12:          c 2018-05-11
13:          c 2018-06-11
14:          c 2018-07-11

对于循环生成R中日期之间的月份

4 个答案:

代码

数据