Force argument to have quotes

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Bert
Gunter
Sent: Tuesday, June 06, 2017 12:14 PM
To: Doran, Harold
Cc: r-help at r-project.org
Subject: Re: [R] Force argument to have quotes

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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