count.tbl_lazy function

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()
db %>% count(g, wt = x) %>% show_query()
db %>% count(g, wt = x, sort = TRUE) %>% show_query()