group_by solutions

group_by-solutions.R

# group_by

![](slides/images/group-by.png)


`summarize` becomes truly powerful when paired with `group_by`, which enables us to perform calculations on each group. 

Calculate the mean hours of sleep for females and males using `group_by` and `summarize`.

```{r}
nhanes %>% 
  group_by(gender) %>% 
  summarize(mean_hours_sleep = mean(sleep_hrs_night, na.rm = TRUE))
```

We can use `group_by` with multiple groups.

Use `group_by` for `gender` and `work` (whether or not respondents are working) before calculating mean hours of sleep.

```{r}
nhanes %>% 
  group_by(gender, work) %>% 
  summarize(mean_hours_sleep = mean(sleep_hrs_night, na.rm = TRUE),
            number_of_observations = n())
```