Mutate using Date Column

[HTP]

Hello everyone!

Suppose that I have 2019 data with the average daily revenues of a small business. So there are 365 rows in the data representing each day in a year (i.e., there are 365 days in a year), and it looks something like this:

Day	Date	Revenue
1	2019-01-01	1700
2	2019-01-02	1400
3	2019-01-03	1800
4	2019-01-04	900
5	2019-01-05	2000
.	.	.
.	.	.
.	.	.
364	2019-12-30	3000
365	2019-12-31	3800

I wanna create another column called "Season" using the mutate function. More specifically, the December 1 to February 31 would be labeled "Winter", March 1 to May 31 would be "Spring", June 1, to August 31 would be "Summer", and September 1 to November 31 would be "Fall." So I wanna create something like this:

Day	Date	Revenue	Season
1	2019-01-01	1700	Winter
2	2019-01-02	1400	Winter
3	2019-01-03	1800	Winter
4	2019-01-04	900	Winter
5	2019-01-05	2000	Winter
.	.	.
.	.	.
59	2019-03-01	1900	Spring
60	2019-03-02	1850	Spring
.	.	.
.	.	.
151	2019-06-01	2100	Summer
152	2019-06-02	2000	Summer
.	.	.
.	.	.
243	2019-09-01	2300	Fall
244	2019-09-02	1900	Fall
.	.	.
.	.	.
364	2019-12-30	3000	Winter
365	2019-12-31	3800	Winter

So anybody know how to do this? I reckon this would be quite simple, but I have never used the mutate function using the date, so I'm not sure how to do this.

Thank you,

[dvetsch75]

This is a really good use case for dplyr::case_when. I would do something like this:

data %>% 
    mutate(
        season = case_when(
            lubridate::month(date) %in% c(12, 1, 2) ~ 'Winter',
            lubridate::month(date) %in% 3:5 ~ 'Spring',
            lubridate::month(date) %in% 6:8 ~ 'Summer',
            lubridate::month(date) %in% 9:11 ~ 'Fall'
        )
    )