tally() is a convenient wrapper for summarise that will either call
sum(n) depending on whether you're tallying
for the first time, or re-tallying.
count() is similar but calls
group_by() before and
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
mutate() is to
they add an additional column rather than collapsing each group.
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(Optional) If omitted (and no variable named
The output column name. If omitted, it will be
Variables to group by.
A tbl, grouped the same way as
The column name in the returned data is usually
n, even if you
have supplied a weight.
If the data already has a column named
n, the output column
will be called
nn. If the table already has columns called
then the column returned will be
nnn, and so on.
To control the output column name use
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# tally() is short-hand for summarise() mtcars %>% tally() mtcars %>% group_by(cyl) %>% 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) # Change the name of the newly created column: species <- starwars %>% count(species, homeworld, sort = TRUE, name = "n_species_by_homeworld") species species %>% count(species, sort = TRUE, name = "n_species") # add_count() is useful for groupwise filtering # e.g.: show details for species that have a single member starwars %>% add_count(species) %>% filter(n == 1)
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