Wrappers to dplyr's data modification functions like arrange, select,... that work with string arguments.

s_dplyr

# 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
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)")

I found this gist while looking for a way to use strings of variable names (or even a vector of variable names as strings) with dplyr functions, but it turns out that a lot of this has since been incorporated directly into dplyr. See the "non-standard evaluation" vignette in recent versions:
vignette("nse", package="dplyr")

I agree that this was much-needed functionality, and these are some great little utility functions: thanks for sharing.

I like it. It inspired me to try my hand at standard evaluation adapters for dplyr 0.7.0 using the new rlang / tidyeval notation. Mostly I am trying to keep to column names, so deliberately I have only made arrange_se() nearly as flexible as your s_arrange(). I finally found my notes linking to the page and belatedly added a credit to my project (sorry about the delay).