Count observations by group

These are methods for the dplyr count() and tally() generics. They wrap up group_by.tbl_lazy(), summarise.tbl_lazy() and, optionally, arrange.tbl_lazy().

# S3 method for class 'tbl_lazy'
count(x, ..., wt = NULL, sort = FALSE, name = NULL)

# S3 method for class 'tbl_lazy'
add_count(x, ..., wt = NULL, sort = FALSE, name = NULL, .drop = NULL)

# S3 method for class 'tbl_lazy'
tally(x, wt = NULL, sort = FALSE, name = NULL)

Arguments

x

A data frame, data frame extension (e.g. a tibble), or a lazy data frame (e.g. from dbplyr or dtplyr).

...

<data-masking> Variables, or functions of variables. Use desc() to sort a variable in descending order.

wt

<data-masking> Frequency weights. Can be NULL or a variable:

• If NULL (the default), counts the number of rows in each group.

• If a variable, computes sum(wt) for each group.

sort

If TRUE, will show the largest groups at the top.

name

The name of the new column in the output.

If omitted, it will default to n. If there's already a column called n, it will use nn. If there's a column called n and nn, it'll use nnn, and so on, adding ns until it gets a new name.

.drop

Not supported for lazy tables.

Examples

library(dplyr, warn.conflicts = FALSE)

db <- memdb_frame(g = c(1, 1, 1, 2, 2), x = c(4, 3, 6, 9, 2))
db %>% count(g) %>% show_query()
#> <SQL>
#> SELECT `g`, COUNT(*) AS `n`
#> FROM `dbplyr_jRmVMuJacg`
#> GROUP BY `g`
db %>% count(g, wt = x) %>% show_query()
#> <SQL>
#> SELECT `g`, SUM(`x`) AS `n`
#> FROM `dbplyr_jRmVMuJacg`
#> GROUP BY `g`
db %>% count(g, wt = x, sort = TRUE) %>% show_query()
#> <SQL>
#> SELECT `g`, SUM(`x`) AS `n`
#> FROM `dbplyr_jRmVMuJacg`
#> GROUP BY `g`
#> ORDER BY `n` DESC