1.12

The dplyr::summarize is often used in conjunction with the group_by function, to calculate statistics by group.

# calculate mean height and weight by gender
newdata <- group_by(starwars, gender)
newdata <- summarize(newdata, 
                     mean_ht = mean(height, na.rm=TRUE), 
                     mean_wt = mean(mass, na.rm=TRUE))
newdata

## # A tibble: 3 × 3
##   gender    mean_ht mean_wt
##   <chr>       <dbl>   <dbl>
## 1 feminine     167.    54.7
## 2 masculine    177.   107. 
## 3 <NA>         175     81