tally {dplyr} | R Documentation |
tally()
is a convenient wrapper for summarise that will either call
n()
or sum(n)
depending on whether you're tallying
for the first time, or re-tallying. count()
is similar but calls
group_by()
before and ungroup()
after.
add_tally()
adds a column n
to a table based on the number
of items within each existing group, while add_count()
is a shortcut that
does the grouping as well. These functions are to tally()
and count()
as mutate()
is to summarise()
:
they add an additional column rather than collapsing each group.
tally(x, wt, sort = FALSE) count(x, ..., wt = NULL, sort = FALSE) add_tally(x, wt, sort = FALSE) add_count(x, ..., wt = NULL, sort = FALSE)
x |
a |
wt |
(Optional) If omitted (and no variable named |
sort |
if |
... |
Variables to group by. |
A tbl, grouped the same way as x
.
The column name in the returned data is usually n
, even if you
have supplied a weight.
If the data already already has a column named n
, the output column
will be called nn
. If the table already has columns called n
and nn
then the column returned will be nnn
, and so on.
There is currently no way to control the output variable name - if you
need to change the default, you'll have to write the summarise()
yourself.
# tally() is short-hand for summarise() mtcars %>% tally() # count() is a short-hand for group_by() + tally() mtcars %>% count(cyl) # add_tally() is short-hand for mutate() mtcars %>% add_tally() # add_count() is a short-hand for group_by() + add_tally() mtcars %>% add_count(cyl) # count and tally are designed so that you can call # them repeatedly, each time rolling up a level of detail species <- starwars %>% count(species, homeworld, sort = TRUE) species species %>% count(species, sort = TRUE) # add_count() is useful for groupwise filtering # e.g.: show only species that have a single member starwars %>% add_count(species) %>% filter(n == 1)