在数据帧列表中提取季节

Question

我有一个数据帧列表，例如

library(lubridate)
df1 = data.frame (Date = seq(ymd('2005-04-16'),ymd('2016-10-15'),by='day'), 
                  Station1423 = replicate(1,sample(0:130, 4201,rep=TRUE)))
df2 = data.frame (Date = seq(ymd('2001-09-02'),ymd('2018-12-31'),by='day'), 
                  Station4322 = replicate(1,sample(0:130, 6330,rep=TRUE)))
df3 = data.frame (Date = seq(ymd('1995-02-20'),ymd('2018-12-31'),by='day'), 
                  Station1242 = replicate(1,sample(0:130, 8716,rep=TRUE)))

dflist = list(df1, df2, df3)
names(dflist) = c("df1", "df2", "df3")

我现在想提取列表中每个数据框的季节。结果应该是这样的嵌套列表：

dflist    list of 3
   df1       list of 4
     DJF: dataframe
     ..$Date
     ..$Station1423   
     JJA: dataframe
     ..$Date
     ..$Station1423   
     MAM: dataframe
     ..$Date
     ..$Station1423 
     SON: dataframe
     ..$Date
     ..$Station1423     
 df2       list of 4
     DJF: dataframe
     ..$Date
     ..$Station4322   
     JJA: dataframe
     ..$Date
     ..$Station4322   
.....and so on

我也可以使用像这样的简单列表：

dflist    list of 12
  df1_DJF: dataframe
      ..$Date
      ..$Station1423 
  df1_JJA: dataframe
......

Answer 1

构建一个将季节编码为一个月的数据框。

seasons <- tibble(month = 1:12, season = c(rep("DJF", 2), rep("MAM", 3), rep("JJA", 3), rep("SON", 3), "DJF"))

使用map按月加入每个数据框，然后split加入季节。

library(lubridate)
library(purrr)
library(dplyr)

new_list <- dflist %>%
  map( ~ {mutate(., month = month(Date)) %>%
      left_join(seasons, by = "month") %>%
      split(f = .$season)
  })

请注意，这向原始数据框添加了两列。我们可以再次使用 map 轻松删除它们。

new_list %>%
  map_depth(.depth = 2, ~ select(., -month, - season))

或者在原来的基础上嵌套另一个map。

new_list <- dflist %>%
  map( ~ {mutate(., month = month(Date)) %>%
      left_join(seasons, by = "month") %>%
      split(f = .$season) %>%
      map(~ select(., -month, -season))
  })

在数据帧列表中提取季节

Extracting Seasons in list of Dataframes

r

extract

list

dataframe

lubridate