Aggregates over a discrete field — db_compute

Uses dplyr operations to aggregate data. Because of this approach, the calculations automatically run inside the database if `data` has a database or sparklyr connection. The `class()` of such tables in R are: tbl_sql, tbl_dbi, tbl_spark

Usage

db_compute_count(data, x, ..., y = n())

Arguments

data: A table (tbl)
x: A discrete variable
...: A set of named or unnamed aggregations
y: The aggregation formula. Defaults to count (n)

Value

An ungrouped data.frame with the discrete variable and one or more aggregation columns. The first column is the grouping variable (x), followed by the aggregated values.

Examples

# \dontrun{
library(DBI)
library(dplyr)
con <- dbConnect(duckdb::duckdb(), ":memory:")
db_mtcars <- copy_to(con, mtcars, "mtcars")

# Returns the row count per am
db_mtcars |>
  db_compute_count(am)
#> # A tibble: 2 × 2
#>      am `n()`
#>   <dbl> <dbl>
#> 1     0    19
#> 2     1    13

# Returns the average mpg per am
db_mtcars |>
  db_compute_count(am, mean(mpg))
#> Warning: Missing values are always removed in SQL aggregation functions.
#> Use `na.rm = TRUE` to silence this warning
#> This warning is displayed once every 8 hours.
#> # A tibble: 2 × 2
#>      am `mean(mpg)`
#>   <dbl>       <dbl>
#> 1     0        17.1
#> 2     1        24.4

# Returns the average and sum of mpg per am
db_mtcars |>
  db_compute_count(am, mean(mpg), sum(mpg))
#> # A tibble: 2 × 3
#>      am `mean(mpg)` `sum(mpg)`
#>   <dbl>       <dbl>      <dbl>
#> 1     0        17.1       326.
#> 2     1        24.4       317.

dbDisconnect(con)
# }