Overwrite a specific value in a dataframe, based on matching values

Question

My data is in a format like this:

#>   country year value
#> 1     AUS 2019   100
#> 2     USA 2019   120
#> 3     AUS 2018    90

df <- data.frame(stringsAsFactors=FALSE,
     country = c("AUS", "USA", "AUS"),
        year = c(2019, 2019, 2018),
       value = c(100, 120, 90)
)

and I have an one row dataframe that represents a revision that should overwrite the existing record in my data.

#>   country year value
#> 1     AUS 2019   500

df2 <- data.frame(stringsAsFactors=FALSE,
                  country = c("AUS"),
                     year = c(2018),
                    value = c(500)
             )

My desired output is:

#>   country year value
#> 1     AUS 2019   100
#> 2     USA 2019   120
#> 3     AUS 2018   500

I know how to find the row to overwrite:

library(tidyverse)
df %>% filter(country == overwrite$country & year == overwrite$year) %>% 
  mutate(value = overwrite$value)

but how do I put that back in the original dataframe?

Tidyverse answers are easier for me to work with, but I'm open to any solutions.

Answer 1

Using mutate and if_else:

library(tidyverse)

df %>% 
mutate(value = if_else(country %in% df2$country & year %in% df2$year, df2$value, value))

Results in:

country year value
1     AUS 2019   100
2     USA 2019   120
3     AUS 2018   500