Question

我有一个数据集，它有一个名为month的变量，每个月都作为一个字符。是否有一种方法可以将dplyr组合几个月来创建一个季节变量？我尝试过以下但是收到了错误：

data %>%
  mutate(season = ifelse(month[1:3], "Winter", ifelse(month[4:6], "Spring", 
                     ifelse(month[7:9], "Summer", 
                            ifelse(month[10:12], "Fall", NA)))))

有错误：

Error in mutate_impl(.data, dots) : Column `season` must be length 100798 (the number of rows) or one, not 3

我是R的新手，所以非常感谢任何帮助！

Answer 1

当有多个键/值时，我们可以使用键/ val数据集

进行连接

keyval <- data.frame(month = month.abb, 
      season = rep(c("Winter", "Spring", "Summer", "Fall"), each = 3),
      stringsAsFactors = FALSE)

left_join(data, keyval)

Answer 2

正确的语法应该是

data %>% mutate(season = ifelse(month %in% 10:12, "Fall",
                               ifelse(month %in% 1:3, "Winter",
                                      ifelse(month %in% 4:6, "Spring",
                                             "Summer"))))

修改：可能是完成工作的更好方法

temp_data %>%
  mutate(
    season = case_when(
      month %in% 10:12 ~ "Fall",
      month %in%  1:3  ~ "Winter",
      month %in%  4:6  ~ "Spring",
      TRUE ~ "Summer"))

Answer 3

您也可以尝试使用dplyr::recode或forcats中的功能。我认为这是最简单的方法：

library(tidyverse)
library(lubridate)
#> 
#> Attaching package: 'lubridate'
#> The following object is masked from 'package:base':
#> 
#>     date
data <- tibble(month = c("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"))

data %>%
  mutate(
    season = fct_collapse(
      .f = month,
      Spring = c("Mar", "Apr", "May"),
      Summer = c("Jun", "Jul", "Aug"),
      Autumn = c("Sep", "Oct", "Nov"),
      Winter = c("Dec", "Jan", "Feb")
    )
  )
#> # A tibble: 12 x 2
#>    month season
#>    <chr> <fct> 
#>  1 Jan   Winter
#>  2 Feb   Winter
#>  3 Mar   Spring
#>  4 Apr   Spring
#>  5 May   Spring
#>  6 Jun   Summer
#>  7 Jul   Summer
#>  8 Aug   Summer
#>  9 Sep   Autumn
#> 10 Oct   Autumn
#> 11 Nov   Autumn
#> 12 Dec   Winter

由reprex package（v0.2.0）创建于2018-04-06。

使用R中的dplyr按月创建季节变量

3 个答案: