How to sort data in descending order based on every second value in R?

I am using dplyr for most of my data wrangling in R. Yet, I am having a hard time achieving this particular effect. Can’t also seem to find the answer by googling either.

Assume I have data like this and what I want to achieve is to sort person-grouped data based on cash value from the year 2021. Below I show the outcome I wish to achieve. I am just missing my imagination on this one I guess. If I only had 2021 value I could simply use ... %>% arrange(desc(cash)) but I am not sure how to follow from here.

    year   person        cash
0   2020   personone     29
1   2021   personone     40
2   2020   persontwo     17
3   2021   persontwo     13
4   2020   personthree   62
5   2021   personthree   55      

And what I want to achieve is to sort this data in descending order based on values from the year 2021. So that the data should look like:

    year   person        cash
0   2020   personthree   62
1   2021   personthree   55
2   2020   personone     29
3   2021   personone     40
4   2020   persontwo     17
5   2021   persontwo     13   

>Solution :

One approach using a join:

df %>%
  filter(year == 2021) %>%
  # group_by(person) %>% slice(2) %>% ungroup() %>%  #each person's yr2
  arrange(-cash) %>%
  select(-cash, -year) %>%
  left_join(df)

Output:

       person year cash
1 personthree 2020   62
2 personthree 2021   55
3   personone 2020   29
4   personone 2021   40
5   persontwo 2020   17
6   persontwo 2021   13