dplyr's ungroup function

ungroup_example.Rmd

# {dplyr}'s `ungroup()` function

```{r}
# packages
library(gapminder)
library(dplyr)
```

In this example, we calculate the difference in a country's life expectancy from the continent's mean life expectancy
 - for example, the difference between life expectancy in Canada and the mean life expectancy of countries in the Americas

Step 1:

* Filter for 2007

* Then group by continent and 

* Mutate to get the mean continental life expectancy

```{r}
gapminder %>%
  filter(year == 2007) %>% 
  group_by(continent) %>%
  mutate(lifeExp_mean = mean(lifeExp))
```

By adding the `ungroup()` function, we revert to the country-level data frame but now with the continent mean as a variable

And then we can append another mutate to calculate the difference

```{r}
gapminder %>%
  filter(year == 2007) %>% 
  group_by(continent) %>%
  mutate(lifeExp_mean = mean(lifeExp)) %>%
  # 
  ungroup() %>% 
  mutate(lifeExp_diff = lifeExp - lifeExp_mean)
```

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