R: Filter within a selection of variables

filter_all {dplyr}

R Documentation

Filter within a selection of variables

Description

These scoped filtering verbs apply a predicate expression to a selection of variables. The predicate expression should be quoted with all_vars() or any_vars() and should mention the pronoun . to refer to variables.

Usage

filter_all(.tbl, .vars_predicate, .preserve = FALSE)

filter_if(.tbl, .predicate, .vars_predicate, .preserve = FALSE)

filter_at(.tbl, .vars, .vars_predicate, .preserve = FALSE)

Arguments

`.tbl`	A `tbl` object.
`.vars_predicate`	A quoted predicate expression as returned by `all_vars()` or `any_vars()`. Can also be a function or purrr-like formula. In this case, the intersection of the results is taken by default and there's currently no way to request the union.
`.preserve`	when `FALSE` (the default), the grouping structure is recalculated based on the resulting data, otherwise it is kept as is.
`.predicate`	A predicate function to be applied to the columns or a logical vector. The variables for which `.predicate` is or returns `TRUE` are selected. This argument is passed to `rlang::as_function()` and thus supports quosure-style lambda functions and strings representing function names.
`.vars`	A list of columns generated by `vars()`, a character vector of column names, a numeric vector of column positions, or `NULL`.

Grouping variables

The grouping variables that are part of the selection are taken into account to determine filtered rows.

Examples

# While filter() accepts expressions with specific variables, the
# scoped filter verbs take an expression with the pronoun `.` and
# replicate it over all variables. This expression should be quoted
# with all_vars() or any_vars():
all_vars(is.na(.))
any_vars(is.na(.))


# You can take the intersection of the replicated expressions:
filter_all(mtcars, all_vars(. > 150))

# Or the union:
filter_all(mtcars, any_vars(. > 150))


# You can vary the selection of columns on which to apply the
# predicate. filter_at() takes a vars() specification:
filter_at(mtcars, vars(starts_with("d")), any_vars((. %% 2) == 0))

# And filter_if() selects variables with a predicate function:
filter_if(mtcars, ~ all(floor(.) == .), all_vars(. != 0))


# We're working on a new syntax to allow functions instead,
# including purrr-like lambda functions. This is already
# operational, but there's currently no way to specify the union of
# the predicate results:
mtcars %>% filter_at(vars(hp, vs), ~ . %% 2 == 0)

[Package dplyr version 0.8.5 Index]