[R] Force argument to have quotes

[Bert Gunter]

Harold:

As a general rule, if you are using eval(parse(...)) you are doing it
poorly in R; cf

library("fortunes")
fortune(106)

Why is something like this not suitable:

fun1 <- function(a1,a2,a3 = c("hi","by"))
{
   cat(a3,a1+a2,"\n")
}

> fun1 (1,2)
hi by 3
> fun1(1,2, a3 = "whoopee")
whoopee 3

... or, if you want to include the function as an argument of a list:

> myArgs <- list(fun=fun1, arglist=list(a1=2, a2 =5, a3 = c("hi","by")))

For which you can do stuff like:

> do.call(myArgs[[1]],myArgs[-1][[1]])
hi by 7

> arglist <- myArgs[-1][[1]][-3]
> do.call(myArgs[[1]],c(arglist,a3 = "whoopee"))
whoopee 7

etc. etc.
See ?do.call

Cheers,
Bert



Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Tue, Jun 6, 2017 at 8:01 AM, Doran, Harold <HDoran at air.org> wrote:
> I am writing a program where non-technical R users will read in a config file and the config file will then parse the arguments found within the config and pass them to respective functions. I'm having trouble (efficiently) writing a piece of code to retain quotation marks around the argument which requires it as input, as found in the example function below, myFuncton1.
>
> Below is a minimal, reproducible example of the issue with comments.
>
> ### This is a sample structure of the configuration file
>
> scoreConfig <- structure(list(Function = c("myFunction1", "myFunction1", "myFunction1",
> "myFunction2", "myFunction2"), Argument = c("arg1", "arg2", "arg3",
> "arg1", "arg2"), Value = c("5", "10", "Hello", "5", "10"), Class = c("numeric",
> "numeric", "character", "numeric", "numeric")), .Names = c("Function",
> "Argument", "Value", "Class"), class = "data.frame", row.names = c(NA,
> -5L))
>
> ### Two sample functions, once of which requires a string
> myFunction1 <- function(arg1, arg2, arg3 = c('Hello', 'Goodbye')){
>         arg3 <- match.arg(arg3)
>         result <- arg1 + arg2
>         cat(arg3, result, '\n')
>         }
>
>
> myFunction2 <- function(arg1, arg2){
>         result <- arg1 * arg2
>         result
>         }
>
>
> ### Working Example.
> ### myFunction2 works no problem
> myFunction2Vals <- subset(scoreConfig, Function == 'myFunction2')
> myOptions <- with(myFunction2Vals, paste(Argument, Value, sep = '=', collapse = ','))
> eval(parse(text = paste( "myFunction2(", myOptions, ")" )))
>
>
> ### myFunction1 fails
> myFunction1Vals <- subset(scoreConfig, Function == 'myFunction1')
> myOptions <- with(myFunction1Vals, paste(Argument, Value, sep = '=', collapse = ','))
> eval(parse(text = paste( "myFunction1(", myOptions, ")" )))
>
> ### What I want is simply
> myFunction1(arg1 = 1, arg2 = 2, arg3 = 'Hello')
>
> I'm curious if someone has a perspective on the most efficient way to automate this by using information provided in the 'Value" column, so perhaps conditional on that value it could wrap the name in quotes.
>
> I admit to running into a limit and am tapping out so to speak on the right way to do this.
>
> Thanks for any advice
> Harold
>
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