R/s_dplyr.r

In skranz/modify: modify is a function to augment dplyr for quick replacement by reference as in data.table

# Helper functions that allow string arguments for dplyr's data modification functions like arrange, select etc.
# Author: Sebastian Kranz
 
# Examples are below
 
#' Modified version of dplyr's filter that uses string arguments
#' @export
s_filter = function(.data, ...) {
eval.string.dplyr(.data,"filter", ...)
}
 
#' Modified version of dplyr's select that uses string arguments
#' @export
s_select = function(.data, ...) {
eval.string.dplyr(.data,"select", ...)
}
 
#' Modified version of dplyr's arrange that uses string arguments
#' @export
s_arrange = function(.data, ...) {
eval.string.dplyr(.data,"arrange", ...)
}
 
#' Modified version of dplyr's arrange that uses string arguments
#' @export
s_mutate = function(.data, ...) {
eval.string.dplyr(.data,"mutate", ...)
}
 
#' Modified version of dplyr's summarise that uses string arguments
#' @export
s_summarise = function(.data, ...) {
eval.string.dplyr(.data,"summarise", ...)
}
 
#' Modified version of dplyr's group_by that uses string arguments
#' @export
s_group_by = function(.data, ...) {
eval.string.dplyr(.data,"group_by", ...)
}
 
# Internal function used by s_filter, s_select etc.
eval.string.dplyr = function(.data, .fun.name, ...) {
  args = list(...)
  args = unlist(args)
  code = paste0(.fun.name,"(.data,", paste0(args, collapse=","), ")")
  df = eval(parse(text=code,srcfile=NULL))
  df
}

examples.sfilter = function() {
  # Examples
  library(dplyr)
   
  # Original usage of dplyr
  mtcars %.%
  filter(gear == 3,cyl == 8) %.%
  select(mpg, cyl, hp:vs)
   
  # Select user specified cols.
  # Note that you can have a vector of strings
  # or a single string separated by ',' or a mixture of both
  cols = c("mpg","cyl, hp:vs")
  mtcars %.%
  filter(gear == 3,cyl == 8) %.%
  s_select(cols)
   
  # Filter using a string
  col = "gear"
  mtcars %.%
  s_filter(paste0(col,"==3"), "cyl==8" ) %.%
  select(mpg, cyl, hp:vs)
   
  # Arrange without using %.%
  s_arrange(mtcars, "-mpg, gear, carb")
   
  # group_by and summarise with strings
  mtcars %.%
  s_group_by("cyl") %.%
  s_summarise("mean(disp), max(disp)")
}