dynutils (version 1.0.11)

mapdf: Apply a function to each row of a data frame

Description

The mapdf functions transform their input by applying a function to each row of a data frame and returning a vector the same length as the input. These functions work a lot like purrr's map() functions.

Usage

mapdf(.x, .f, ...)
mapdf_lgl(.x, .f, ...)
mapdf_chr(.x, .f, ...)
mapdf_int(.x, .f, ...)
mapdf_dbl(.x, .f, ...)
mapdf_dfr(.x, .f, ...)
mapdf_dfc(.x, .f, ...)
mapdf_lat(.x, .f, ...)
walkdf(.x, .f, ...)

Arguments

.x

A data.frame, data_frame, or tibble.

.f

A function or formula. If a function, the first argument will be the row as a list. If a formula, e.g. ~ .$a, the . is a placeholder for the row as a list.

...

Additional arguments passed on to the mapped function.

Details

• mapdf() always returns a list.

• mapdf_lgl(), mapdf_int(), mapdf_dbl() and mapdf_chr() return vectors of the corresponding type (or die trying).

• mapdf_dfr() and mapdf_dfc() return data frames created by row-binding and column-binding respectively. They require dplyr to be installed.

• mapdf_lat() returns a tibble by transforming outputted lists to a tibble using list_as_tibble.

• walkdf() calls .f for its side-effect and returns the input .x.

Examples

library(dplyr)

tib <- tibble(
  a = c(1, 2),
  b = list(log10, sqrt),
  c = c("parrot", "quest"),
  .object_class = list(c("myobject", "list"), c("yourobject", "list"))
)

# map over the rows using a function
tib %>% mapdf(class)

# or use an anonymous function
tib %>% mapdf(function(row) paste0(row$b(row$a), "_", row$c))

# or a formula
tib %>% mapdf(~ .$b)

# there are many more variations available
# see ?mapdf for more info
tib %>% mapdf_lgl(~ .$a > 1)
tib %>% mapdf_chr(~ paste0("~", .$c, "~"))
tib %>% mapdf_int(~ nchar(.$c))
tib %>% mapdf_dbl(~ .$a * 1.234)