How to parametrize function calls in dplyr 0.7?

by

dplyr will have a specialized group_by function group_by_at to deal with multiple grouping variables. It would be much easier to use the new member of the _at family:

# using the pre-release 0.6.0

cols <- c("am","gear")

mtcars %>%
    group_by_at(.vars = cols) %>%
    summarise(mean_cyl=mean(cyl))

# Source: local data frame [4 x 3]
# Groups: am [?]
# 
# am  gear mean_cyl
# <dbl> <dbl>    <dbl>
# 1     0     3 7.466667
# 2     0     4 5.000000
# 3     1     4 4.500000
# 4     1     5 6.000000

The .vars argument accepts both character/numeric vector or column names generated by vars:

.vars

A list of columns generated by vars(), or a character vector of
column names, or a numeric vector of column positions.

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