summarise_dt: Summarise columns to single values
In hope-data-science/tidydt0: Tidy Verbs for `data.table`

Description Usage Arguments Value See Also Examples

Analogous function for summarise and summarise_all in dplyr.

summarise_dt(data, ..., by, keyby, fun = NULL)

summarize_dt(data, ..., by, keyby, fun = NULL)

summarise_all_dt(data, fun, by, keyby)

summarize_all_dt(data, fun, by, keyby)

`data`	data.frame
`...`	List of variables or name-value pairs of summary/modifications functions.
`by`	unquoted name of grouping variable of list of unquoted names of grouping variables. For details see data.table
`keyby`	Same as `by`, but with an additional `setkey()` run on the by columns of the result, for convenience. It is common practice to use 'keyby=' routinely when you wish the result to be sorted. For details see data.table.
`fun`	function which will be applied to all variables in `dt_summarize` and `dt_summarize_all`.

data.table

summarise,dt_summarise, summarise_all,dt_summarise_all

iris %>% summarise_dt(avg = mean(Sepal.Length))
iris %>% summarise_dt(avg = mean(Sepal.Length),by = Species)
mtcars %>% summarise_dt(avg = mean(hp),by = .(cyl,vs))

# the data.table way
mtcars %>% summarise_dt(cyl_n = .N, by = .(cyl, vs)) # `.`` is short for list

iris %>%summarise_all_dt(fun = mean,by = Species)