```r
mean_height = starwars %>%
  group_by(species) %>%
  summarise(mean(height))

class(mean_height)
```

```
## [1] "tbl_df"     "tbl"        "data.frame"
```

```r
head(mean_height)
```

```
## # A tibble: 6 x 2
##   species  `mean(height)`
##   <chr>             <dbl>
## 1 Aleena               79
## 2 Besalisk            198
## 3 Cerean              198
## 4 Chagrian            196
## 5 Clawdite            168
## 6 Droid                NA
```