gistfile1.r

foo <- function(data_frame, column, regex, ...){

    #Run the regex over the column and add a new column to the object noting whether the value in that row matched or not
    data_frame$matched <- grepl(x = data_frame[,column], pattern = regex, ...)

    #Return
    return(data_frame)
}

#Call. Works like a charm!
foo(data_frame = x, column = "vegetables", regex = "turnips")

#Hmn. Except you need PCRE for certain types of regex. "perl" is a parameter in grepl.
foo(data_frame = x, column = "vegetables", regex = "turnip(s)?", perl = TRUE)

#Some people are assholes. Those people submit data. Asshole-submitted data does not respect CAPS LOCK.
foo(data_frame = x, column = "vegetables", regex = "turnip(s)?", perl = TRUE, ignore.case = TRUE)

#And some people might find it funny to literally insert "turnip(s)?" to try and blow something in the system
foo(data_frame = x, column = "vegetables", regex = "turnip(s)?", perl = TRUE, ignore.case = TRUE, fixed = TRUE)

#And all of these parameters slow it down so we probably want it to ignore multi-byte characters
foo(data_frame = x, column = "vegetables", regex = "turnip(s)?", perl = TRUE, ignore.case = TRUE, fixed = TRUE, useBytes = TRUE)

#"..." allows me to pass whatever arguments I need for a particular regex or a particular object through. The alternative would be defining the function as...
foo <- function(data_frame, column, regex, perl = FALSE, ignore.case = FALSE, fixed = FALSE, useBytes = FALSE){

    #Run the regex over the column and add a new column to the object noting whether the value in that row matched or not
    data_frame$matched <- grepl(x = data_frame[,column], pattern = regex, perl = perl, ignore.case = ignore.case, fixed = fixed, useBytes = useBytes)

    #Return
    return(data_frame)
}
#...and that's just ugly.