返回數據框中R中最小日期和最大日期之間的采樣日期

Question

如何在數據框中的R中的最小日期和最大日期之間返回采樣日期作為附加列？

Course MinEnrollmentDate MaxEnrollmentDate
Maths 3/11/2016 3/4/2016
Chemistry 6/11/2016 6/4/2016
Physics 9/11/2016 9/4/2016
English 12/11/2016 12/4/2016
Science 3/11/2017 3/4/2017

Answer 1

使用dplyr我們可以做到：

library(dplyr)

df <- df %>% 
    rowwise() %>% 
    mutate(MinEnrollmentDate = as.Date(MinEnrollmentDate, format = '%m/%d/%Y'),
           MaxEnrollmentDate = as.Date(MaxEnrollmentDate, format = '%m/%d/%Y'), 
           sampleDate = sample(seq(MinEnrollmentDate, MaxEnrollmentDate, '-1 day'), 1))

df
#> Source: local data frame [5 x 4]
#> Groups: <by row>
#> 
#> # A tibble: 5 x 4
#>      Course MinEnrollmentDate MaxEnrollmentDate  sampleDate
#>       <chr>            <date>            <date>      <date>
#> 1     Maths        2016-03-11        2016-03-04  2016-03-08
#> 2 Chemistry        2016-06-11        2016-06-04  2016-06-09
#> 3   Physics        2016-09-11        2016-09-04  2016-09-06
#> 4   English        2016-12-11        2016-12-04  2016-12-09
#> 5   Science        2017-03-11        2017-03-04  2017-03-06

不知道我的日期格式是否正確，是否模棱兩可，請隨時更正format=部分。 數據：

df <-  read.table(text = 'Course MinEnrollmentDate MaxEnrollmentDate
                  Maths 3/11/2016 3/4/2016
                  Chemistry 6/11/2016 6/4/2016
                  Physics 9/11/2016 9/4/2016
                  English 12/11/2016 12/4/2016
                  Science 3/11/2017 3/4/2017', header = T, stringsAsFactors = F)

Answer 2

您可以計算兩個日期之間的天數：

days <- as.Date(data$MinEnrollmentDate, format="%d/%m/%Y") - as.Date(data$MaxEnrollmentDate, format="%d/%m/%Y")

然后添加對MinEnrollmentDate 1之間和天到數的隨機數MaxEnrollmentDate與功能sample()

for(i in seq_along(days)) {
  data[i,4] <- as.character(as.Date(data$MinEnrollmentDate, format="%d/%m/%Y")[i] + sample(1:days[i],1))
}

Answer 3

假設您正在使用名為mydata的數據框，則可以使用以下代碼段：

mydata$sampledate <- sample(seq(as.Date(mydata$MinEnrollmentDate), as.Date(mydata$MinEnrollmentDate), by="day"), 1)

基本上，這是首先生成一個從開始日期到結束日期的全天序列，然后從該序列中隨機抽取一個大小為1的樣本，並將其寫入您的數據框。

Answer 4

為了完整起見，請逐步lubridate解決方案（使用GGamba的df）：

if (!require(lubridate)) {
  install.packages("lubridate")
}

df <-  read.table(text = 'Course MinEnrollmentDate MaxEnrollmentDate
                  Maths 3/11/2016 3/4/2016
                  Chemistry 6/11/2016 6/4/2016
                  Physics 9/11/2016 9/4/2016
                  English 12/11/2016 12/4/2016
                  Science 3/11/2017 3/4/2017', header = T, stringsAsFactors = F)

no_days <- as.POSIXct(df$MinEnrollmentDate, format = "%d/%m/%Y") - as.POSIXct(df$MaxEnrollmentDate, format = "%d/%m/%Y")

random_days <- sapply(no_days, function(x) sample(x = 1:x, size = 1, replace = T) )

df$random_date <- as.POSIXct(df$MinEnrollmentDate, format = "%d/%m/%Y") + days(random_days)