Formula based version of lapply and sapply

This function is a wrapper for calling lapply on the list resulting from first calling splitBy.

lapply_by(data, formula, FUN, ...)

lapplyBy(formula, data = parent.frame(), FUN, ...)

sapply_by(data, formula, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)

sapplyBy(
  formula,
  data = parent.frame(),
  FUN,
  ...,
  simplify = TRUE,
  USE.NAMES = TRUE
)

Arguments

data

A dataframe.

formula

A formula describing how data should be split.

FUN

A function to be applied to each element in the split list, see 'Examples' below.

...

optional arguments to FUN.

simplify

Same as for sapply

USE.NAMES

Same as for sapply

Value

A list.

See also

splitBy, split_by

Author

Søren Højsgaard, sorenh@math.aau.dk

Examples

fun <- function(x) range(x$uptake)
lapplyBy(~Treatment + Type, data=CO2, FUN=fun)
#> $`nonchilled|Quebec`
#> [1] 13.6 45.5
#> 
#> $`chilled|Quebec`
#> [1]  9.3 42.4
#> 
#> $`nonchilled|Mississippi`
#> [1] 10.6 35.5
#> 
#> $`chilled|Mississippi`
#> [1]  7.7 22.2
#> 
sapplyBy(~Treatment + Type, data=CO2, FUN=fun)
#>      chilled|Mississippi chilled|Quebec nonchilled|Mississippi
#> [1,]                 7.7            9.3                   10.6
#> [2,]                22.2           42.4                   35.5
#>      nonchilled|Quebec
#> [1,]              13.6
#> [2,]              45.5

# Same as
lapply(splitBy(~Treatment + Type, data=CO2), FUN=fun)
#> $`chilled|Mississippi`
#> [1]  7.7 22.2
#> 
#> $`chilled|Quebec`
#> [1]  9.3 42.4
#> 
#> $`nonchilled|Mississippi`
#> [1] 10.6 35.5
#> 
#> $`nonchilled|Quebec`
#> [1] 13.6 45.5
#>