Home dplyr: Arrange not behaving as expected after group_by and summarize
 I must be missing something with how group_by levels in dplyr get peeled off. In the example below, I group by 2 columns, summarize values into a single variable, then sort by that new variable: mtcars %>% group_by( cyl, gear ) %>% summarize( hp_range = max(hp) - min(mpg)) %>% arrange( desc(hp_range) ) # Source: local data frame [8 x 3] # Groups: cyl [3] # # cyl gear hp_range # (dbl) (dbl) (dbl) #1 4 4 87.6 #2 4 5 87.0 #3 4 3 75.5 #4 6 5 155.3 #5 6 4 105.2 #6 6 3 91.9 #7 8 5 320.0 #8 8 3 234.6  Obviously this is not sorted by hp_range as intended. What am I missing? EDIT: The example works as expected without the call to desc in arrange. Still unclear why?