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# 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)")
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