Group by aggregate dynamic column name matching

[zx8754]

Instead of below:

df1 %>% 
  group_by(Sepal.Length, Sepal.Width) %>% 
  summarise(mySum = sum(Petal.Length))

I want to be able to do this:

df1 %>% 
  group_by(starts_with("Sepal")) %>% 
  summarise(mySum = sum(Petal.Length))

Reproducible data and code at StackOverflow.

Version: dplyr_0.5.0; R version 3.3.2 (2016-10-31)

[lionel-]

This will be x %>% group_by_at(vars(starts_with("Sepal"))) in the next version.

[zx8754]

Phew that was quick, thank you @lionel- !

OK, this was essentially duplicate of issue #2053 and #2613

[zx8754]

@lionel- Maybe I am asking for impossible (not familiar with internals of dplyr), but would it not be better to make group_by accept column indices, instead of creating a new function group_by_at?

[lionel-]

no, group_by() has mutate semantics, so you can do stuff like group_by(mtcars, as.factor(cyl))