根据月份日期将季节列添加到数据表 [英] Adding a seasons column to data table based on month dates

问题描述

我正在使用data.table，并且试图创建一个名为季节的新列，该列基于名为 MonthName的列创建具有相应季节（例如，夏季，冬季...）的列。

I'm using data.table and I am trying to make a new column, called "season", which creates a column with the corresponding season, e.g summer, winter... based on a column called "MonthName".

我想知道是否有更有效的方法可以根据月份值将季节列添加到数据表中。

I'm wondering whether there is a more efficient way to add a season column to a data table based on month values.

这是300,000个观测值的前6个，假设该表被称为 dt。

This is the first 6 of 300,000 observations, assume that the table is called "dt".

    rrp         Year   Month Finyear hourminute AvgPriceByTOD MonthName
1: 35.27500     1999     1    1999      00:00      33.09037       Jan
2: 21.01167     1999     1    1999      00:00      33.09037       Jan
3: 25.28667     1999     2    1999      00:00      33.09037       Feb
4: 18.42334     1999     2    1999      00:00      33.09037       Feb
5: 16.67499     1999     2    1999      00:00      33.09037       Feb
6: 18.90001     1999     2    1999      00:00      33.09037       Feb

我尝试了以下代码：

dt[, Season :=  ifelse(MonthName = c("Jun", "Jul", "Aug"),"Winter", ifelse(MonthName = c("Dec", "Jan", "Feb"), "Summer", ifelse(MonthName = c("Sep", "Oct", "Nov"), "Spring" , ifelse(MonthName = c("Mar", "Apr", "May"), "Autumn", NA))))]

哪个返回：

 rrp totaldemand   Year Month Finyear hourminute AvgPriceByTOD MonthName Season
1: 35.27500     1999     1    1999      00:00      33.09037       Jan     NA
2: 21.01167     1999     1    1999      00:00      33.09037       Jan Summer
3: 25.28667     1999     2    1999      00:00      33.09037       Feb Summer
4: 18.42334     1999     2    1999      00:00      33.09037       Feb     NA
5: 16.67499     1999     2    1999      00:00      33.09037       Feb     NA
6: 18.90001     1999     2    1999      00:00      33.09037       Feb Summer

我知道了ror：

Warning messages:
1: In MonthName == c("Jun", "Jul", "Aug") :
  longer object length is not a multiple of shorter object length
2: In MonthName == c("Dec", "Jan", "Feb") :
  longer object length is not a multiple of shorter object length
3: In MonthName == c("Sep", "Oct", "Nov") :
  longer object length is not a multiple of shorter object length
4: In MonthName == c("Mar", "Apr", "May") :
  longer object length is not a multiple of shorter object length 

此外，由于我不知道的原因，某些夏季月份被正确地分配为夏季，而其他月份则被分配为不适用，例如行1和2都应该是夏天，但是返回的方式不同。

ALongside this, for reasons that I don't know, some of the summer months are correctly assigned "summer", but others are assigned NA, e.g rows 1 and 2 should both be summer, but return differently.

预先感谢！

推荐答案

一种非常简单的方法是使用查找表将月份名称映射到季节：

One pretty straightforward way is to use a lookup table to map month names to seasons:

# create a named vector where names are the month names and elements are seasons
seasons <- rep(c("winter","spring","summer","fall"), each = 3)
names(seasons) <- month.abb[c(6:12,1:5)] # thanks thelatemail for pointing out month.abb
seasons
#     Jun      Jul      Aug      Sep      Oct      Nov      Dec      Jan 
#"winter" "winter" "winter" "spring" "spring" "spring" "summer" "summer" 
#     Feb      Mar      Apr      May 
#"summer"   "fall"   "fall"   "fall" 

使用它：

dt[, season := seasons[MonthName]]

数据：

dt <- setDT(read.table(text="    rrp         Year   Month Finyear hourminute AvgPriceByTOD MonthName
1: 35.27500     1999     1    1999      00:00      33.09037       Jan
2: 21.01167     1999     1    1999      00:00      33.09037       Jan
3: 25.28667     1999     2    1999      00:00      33.09037       Feb
4: 18.42334     1999     2    1999      00:00      33.09037       Feb
5: 16.67499     1999     2    1999      00:00      33.09037       Feb
6: 18.90001     1999     2    1999      00:00      33.09037       Feb",
   header = TRUE, stringsAsFactors = FALSE))

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