Most data operations are useful when done on groups defined by variables
in the dataset. The group_by
function takes an existing table (or
svy_table) and converts it to a grouped version, where operations are
performed "by group".
A tbl
variables to group by. All tbls accept variable names, some will also accept functions of variables. Duplicated groups will be silently dropped.
By default, when add = FALSE
, group_by
will override
existing groups. To instead add to the existing groups, use add = TRUE
Used to work around non-standard evaluation. See
vignette("nse", package = "dplyr")
for details.
See group_by
for more information about grouping
regular data tables.
On tbl_svy
objects, group_by
sets up the object for
operations similar to those allowed in svyby
.
group_by
for information about group_by on normal data tables.
# Examples of svy_tbl group_by
library(survey)
data(api)
dstrata <- apistrat %>%
as_survey_design(strata = stype, weights = pw) %>%
group_by(stype)
dstrata %>%
summarise(api_diff = survey_mean(api00 - api99))
#> # A tibble: 3 × 3
#> stype api_diff api_diff_se
#> <fct> <dbl> <dbl>
#> 1 E 38.6 2.76
#> 2 H 8.46 3.41
#> 3 M 26.4 3.05