Modify year column : 2008, 2009, 2010 ... becomes 2008, 9, 10...

[budugulo]

In the following example, how do I obtain desired_year from year?

toy_data <- data.frame(
  year = 2008:2017,
  desired_year = c(2008, 9, 10:17)
)

year	desired_year
2008	2008
2009	9
2010	10
2011	11
2012	12
2013	13
2014	14
2015	15
2016	16
2017	17

[Zoe_Turner]

I'm assuming you want 2008 to be 2008 and all the other years to have just the later values so I would use case_when. This is only works if the date is an integer as in your reprex:

library(dplyr)

data <- toy_data %>% 
  mutate(extractedYear = case_when(year == 2008 ~ 2008,
                                   TRUE ~ year - 2000))

If the year in your actual data is in a date format you will need to add the following line of code and you may have to change the equation as the year may come through as something like 20200101:

library(dplyr)

data <- toy_data %>% 
  mutate(Year = as.integer(Year),
                  extractedYear = case_when(year == 2008 ~ 2008,
                                   TRUE ~ year - 2000))

[budugulo]

Many thanks! Just what I wanted