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Filter the First or Last Observation for Each By Group

Source: R/filter_extreme.R
filter_extreme.Rd

Filters the first or last observation for each by group.

Usage

filter_extreme(dataset, by_vars = NULL, order, mode, check_type = "warning")

Arguments

dataset

Input dataset

The variables specified by the order and the by_vars parameter are expected.

by_vars

Grouping variables

Default: NULL

Permitted Values: list of variables created by exprs()

order

Sort order

Within each by group the observations are ordered by the specified order.

Permitted Values: list of variables or desc(<variable>) function calls created by exprs(), e.g., exprs(ADT, desc(AVAL))

mode

Selection mode (first or last)

If "first" is specified, the first observation of each by group is included in the output dataset. If "last" is specified, the last observation of each by group is included in the output dataset.

Permitted Values: "first", "last"

check_type

Check uniqueness?

If "warning" or "error" is specified, the specified message is issued if the observations of the input dataset are not unique with respect to the by variables and the order.

Default: "warning"

Permitted Values: "none", "warning", "error"

Value

A dataset containing the first or last observation of each by group

Details

For each group (with respect to the variables specified for the by_vars parameter) the first or last observation (with respect to the order specified for the order parameter and the mode specified for the mode parameter) is included in the output dataset.

See also

Utilities for Filtering Observations: count_vals(), filter_joined(), filter_relative(), max_cond(), min_cond()

Examples

library(dplyr, warn.conflicts = FALSE)
library(admiral.test)
data("admiral_ex")

# Select first dose for each patient
admiral_ex %>%
  filter_extreme(
    by_vars = exprs(USUBJID),
    order = exprs(EXSEQ),
    mode = "first"
  ) %>%
  select(USUBJID, EXSEQ)
#> # A tibble: 254 x 2
#>    USUBJID     EXSEQ
#>    <chr>       <dbl>
#>  1 01-701-1015     1
#>  2 01-701-1023     1
#>  3 01-701-1028     1
#>  4 01-701-1033     1
#>  5 01-701-1034     1
#>  6 01-701-1047     1
#>  7 01-701-1097     1
#>  8 01-701-1111     1
#>  9 01-701-1115     1
#> 10 01-701-1118     1
#> # … with 244 more rows

# Select highest dose for each patient on the active drug
admiral_ex %>%
  filter(EXTRT != "PLACEBO") %>%
  filter_extreme(
    by_vars = exprs(USUBJID),
    order = exprs(EXDOSE),
    mode = "last",
    check_type = "none"
  ) %>%
  select(USUBJID, EXTRT, EXDOSE)
#> # A tibble: 168 x 3
#>    USUBJID     EXTRT      EXDOSE
#>    <chr>       <chr>       <dbl>
#>  1 01-701-1028 XANOMELINE     81
#>  2 01-701-1033 XANOMELINE     54
#>  3 01-701-1034 XANOMELINE     81
#>  4 01-701-1097 XANOMELINE     54
#>  5 01-701-1111 XANOMELINE     54
#>  6 01-701-1115 XANOMELINE     54
#>  7 01-701-1133 XANOMELINE     81
#>  8 01-701-1146 XANOMELINE     81
#>  9 01-701-1148 XANOMELINE     81
#> 10 01-701-1180 XANOMELINE     81
#> # … with 158 more rows