[Rd] variable problem

Tom McCallum tom.mccallum at levelelimited.com
Tue Nov 7 21:28:45 CET 2006

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


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


Dr. Thomas McCallum
Systems Architect,
Level E Limited
ETTC, The King's Buildings
Mayfield Road,
Edinburgh EH9 3JL, UK
Work  +44 (0) 131 472 4813
Fax:  +44 (0) 131 472 4719
Email: tom at levelelimited.com

Level E is a limited company incorporated in Scotland. The contents of  
this e-mail are privileged and/or confidential. If you are not the  
intended recipient, please
notify the sender and ensure this e-mail is deleted and not read, copied  
or disclosed. It is your responsibility to scan this e-mail and any  
attachments for
computer viruses or other defects. Level E does not accept liability for  
any loss or damage which may result from this e-mail or any attachment.  
E-mail is not secure
and can be intercepted, corrupted or amended. Level E does not accept  
liability for errors or omissions arising as a result of interrupted or  
defective transmission.
Any views, opinions, conclusions or other information in this e-mail which  
do not relate to the business of Level E Limited are not authorised by  
Level E. Unless
specifically stated and authorised by Level E, nothing in this e-mail  
shall be taken to be an offer or acceptance of any contract of any nature.  
E-mail entering or leaving Level E's system is subject to random  
monitoring and recording.

More information about the R-devel mailing list