如何在不同的行中减去两个值，将它们分组为另一个变量？

Question

我有以下数据集

 Month   Year   Hotel_Name   Reviewer_Score  
 8       2015   ambassador         7.711111
 9       2015   ambassador         8.400000
 12      2015   ambassador         9.457890
 2       2016   ambassador         8.398733
 4       2015   nh hotel           8.934023
 7       2015   nh hotel           7.345532
 11      2015   nh hotel           6.893445
 1       2016   nh hotel           8.834923

我想知道每家酒店的第一个分数和最后一个分数之间的差别，并把它们放在Hotel_Name的一个新桌子上。

Answer 1

我不确定你想要第一和最后的分数之间的区别(按日期，最近-最早)还是第一和最后的分数(按数值计算，最多)。

为第一个

library(dplyr)
library(lubridate)
ans1 <- df %>%
         group_by(Hotel_Name) %>%
         arrange(Hotel_Name, parse_date_time(paste(Month, Year), "my")) %>%
         summarise(Diff = abs(last(Reviewer_Score) - first(Reviewer_Score)))

# A tibble: 2 x 2
  # Hotel_Name     Diff
      # <fctr>    <dbl>
# 1 ambassador 0.687622
# 2   nh_hotel 0.099100

第二次

ans2 <- df %>%
         group_by(Hotel_Name) %>%
         summarise(Diff = max(Reviewer_Score) - min(Reviewer_Score))

# A tibble: 2 x 2
  # Hotel_Name     Diff
      # <fctr>    <dbl>
# 1 ambassador 1.746779
# 2   nh_hotel 2.040578

你的数据

df <- read.table(text="Month   Year   Hotel_Name   Reviewer_Score  
 8       2015   ambassador         7.711111
 9       2015   ambassador         8.400000
 12      2015   ambassador         9.457890
 2       2016   ambassador         8.398733
 4       2015   nh_hotel           8.934023
 7       2015   nh_hotel           7.345532
 11      2015   nh_hotel           6.893445
 1       2016   nh_hotel           8.834923", header=TRUE)