How do I efficiently change the values of a vector in a dataframe based off of a current vector in r?

Question

I am trying to create a new vector "seasons" based off of the months vector already provided in my data. I am using the built-in txhousing dataset; I have already filtered the dataframe to only include information on the city of Houston and have called this new dataframe houston.

I have managed to recategorize the twelve months into four seasons, however, the way I did it is not efficient. Does anyone have any suggestions for how I can optimize this code? Whenever I tried to provide a range of months (e.g. houston[houston$month==(3:5),] %<>% mutate(seasons = "spring") I would get the error "In month == 3:5 : longer object length is not a multiple of shorter object length".

Thank you for any help! -an R newbie

houston[houston$month==(1),] %<>% mutate(seasons = "winter")
houston[houston$month==(2),] %<>% mutate(seasons = "winter")
houston[houston$month==(3),] %<>% mutate(seasons = "spring")
houston[houston$month==(4),] %<>% mutate(seasons = "spring")
houston[houston$month==(5),] %<>% mutate(seasons = "spring")
houston[houston$month==(6),] %<>% mutate(seasons = "summer")
houston[houston$month==(7),] %<>% mutate(seasons = "summer")
houston[houston$month==(8),] %<>% mutate(seasons = "summer")
houston[houston$month==(9),] %<>% mutate(seasons = "summer")
houston[houston$month==(10),] %<>% mutate(seasons = "fall")
houston[houston$month==(11),] %<>% mutate(seasons = "fall")
houston[houston$month==(12),] %<>% mutate(seasons = "winter")

[See here](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) on making an R question that folks can help with — camille, Aug 01 '19 at 17:44

score 1 · Accepted Answer · answered Aug 01 '19 at 17:31

dplyr::case_when provides a clean coding for this.

library(dplyr)

# Reprex dataframe (always include one in your questions)
houston <- tibble(month = 1:12)

houston %>%
  mutate(seasons = case_when(month %in% c(1:2, 12) ~ "winter",
                             month %in% 3:5        ~ "spring",
                             month %in% 6:9        ~ "summer",
                             month %in% 10:11      ~ "fall"))

# A tibble: 12 x 2
   month seasons
   <int> <chr>  
 1     1 winter 
 2     2 winter 
 3     3 spring 
 4     4 spring 
 5     5 spring 
 6     6 summer 
 7     7 summer 
 8     8 summer 
 9     9 summer 
10    10 fall   
11    11 fall   
12    12 winter

score 0 · Answer 2 · answered Aug 01 '19 at 17:27

a easy to read and simple way would be like this:

houston[houston$month%in%c(12,2,1),] %<>% mutate(seasons = "winter")
houston[houston$month%in%c(3,4,5),] %<>% mutate(seasons = "spring")
houston[houston$month%in%c(6,7,8),] %<>% mutate(seasons = "summer")
houston[houston$month%in%c(9,10,11),] %<>% mutate(seasons = "fall")

How do I efficiently change the values of a vector in a dataframe based off of a current vector in r?

2 Answers2