[R] How to pass in a list of variables as an argument to a function?

[Randall Goodwin]

Hello,

I have some code that currently works fine and I am endeavoring to
convert the major pieces of it into functions.
This involves taking "hard coded" names of variables that are used in
various places and figuring out how to
abstract them out into functions where the arguments (i.e. a list of
variables) can be passed to the parent function
and used within that function for various purposes.

Here is some code that comes close to replicating some of the cases I
am trying to solve.

Basically,  the same list of variables comes up many times in the
current code (where nothing is really a function).
Now that I am converting everything to a function, I'd like to specify
the list of variables once and use that list
throughout the code in other places.  The list of variables does not
have to be of class = list.  more generally,
it could be any class that can be converted such that it is usable in
paste(), aggregate() and reshape() as in
the example below.

I have tried various things to make it work.. using paste() and
noquote() in combination to build a string that is identical to the
arguments that these functions accept,  however R interprets them as a
string,  not as individual arguments.

Thanks in advance,

Randall

#################################################################

# libraries used
library(reshape)

# create some data similar to use case
myData = data.frame(expand.grid(varA=c("a", "b", "c"),
varB=c("d", "e", "f"),
varC=c("g", "h", "i"),
varD=c("old", "new")),
n=1000, fail=rbinom(2700,1000, 0.01))

# add in one more column
myData$pass = myData$n-myData$fail

# List of grouping vars.  I would like to pass this object around and
use it as arguments in functions
myGroupVars = c("varA", "varB", "varC")

# create a new column that is the combination of the grouping vars
(used in plotting with lattice)
# Question 1:  Is there a way to replace "varA, varB, varC" in the
function below with an object?
myData = transform(myData, groupVar = paste(varA, varB, varC, sep = " | "))

# Sum the data by the same groupVars and two other variables
# Question 2:  Is there a way to replace "varA + varB + varC" in the
function below and do the same aggregation?
myDataSum <- aggregate(cbind(pass, fail) ~ varA + varB + varC +
groupVar + varD, data = myData, sum)

# pivot the pass and fail quantity to one row per group,  labelling them
# Question 3:  This one actually works.  idvar happily accepted the
vector of group vars.  Better way?
myDataSum <- reshape(myDataSum,  idvar = myGroupVars, v.names =
c("pass", "fail"),
timevar = "varD", direction = "wide")