From tom.mccallum at levelelimited.com  Tue Nov  7 21:28:45 2006
From: tom.mccallum at levelelimited.com (Tom McCallum)
Date: Tue, 07 Nov 2006 20:28:45 -0000
Subject: [Rd] variable problem
Message-ID: <op.tinxt7p9ffxks9@norisk>

Hi everyone,

I am not sure this is possible so I would be interested in your  
responses.  Say I have a variable 'v' with the string "myargument" in and  
I have a function 'f' that takes this argument as follows;

f <- function( myargument=5 ) {
   ... does something...
}

Is there anyway I can say something like;

f( v=10 ) such that it will be evaluated as f( myargument=10 ).

I presume there may be some use eval and substitute but if someone could  
point me in the right direction then that would be great.

The end idea is to have a list of m items, declared somewhere else,  which  
can be evaluated as particular arguments named after their list names

e.g

mylist <- list( "a"=1, "b"=2, "c"=3 )

which can be passed to a function taking arguments a,b, or c and it will  
be able to evaluate them accordingly :

long hand this would evaluate to something like
	f( a=mylist[["a"]] );
	f( b=mylist[["b"]] );
	f( c=mylist[["c"]] );

but I would have actually rewritten something like
	for ( myvar in names( mylist ) ) {
		f( some_clever_substitution_to_act_as_argument(myvar) = mylist[[ myvar  
]] );	
	}

I hope I have explained myself clearly enough, if not please say so and I  
will try and give a better example.

Many thanks for your help

Tom



-- 
Dr. Thomas McCallum
Systems Architect,
Level E Limited
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[Rd] variable problem
Tom McCallum