Apply a Function to a Data Frame Split by Factors

By(x, INDICES, FUN, COLUMNS, array = FALSE, ...)

Arguments

x: Data frame
INDICES: Indices (vector or list of indices, vector of column names, or formula of column names)
FUN: A function to be applied to data frame subsets of 'data'.
COLUMNS: (Optional) subset of columns of x to work on
array: if TRUE an array/matrix is always returned
...: Additional arguments to lower-level functions

Details

Simple wrapper of the 'by' function

Author

Klaus K. Holst

Examples

By(datasets::CO2,~Treatment+Type,colMeans,~conc)
#>             Type
#> Treatment    Quebec Mississippi
#>   nonchilled    435         435
#>   chilled       435         435
By(datasets::CO2,~Treatment+Type,colMeans,~conc+uptake)
#> Treatment: nonchilled
#> Type: Quebec
#>      conc    uptake 
#> 435.00000  35.33333 
#> ------------------------------------------------------------ 
#> Treatment: chilled
#> Type: Quebec
#>      conc    uptake 
#> 435.00000  31.75238 
#> ------------------------------------------------------------ 
#> Treatment: nonchilled
#> Type: Mississippi
#>      conc    uptake 
#> 435.00000  25.95238 
#> ------------------------------------------------------------ 
#> Treatment: chilled
#> Type: Mississippi
#>      conc    uptake 
#> 435.00000  15.81429