Re: [R] Very important! Global variables in R?

From: Earl F. Glynn <>
Date: Wed 25 Jan 2006 - 07:39:59 EST

"Sean Davis" <> wrote in message

> > I need urgently your assistance!!!
> > I need a global variable in R. The variable ought to be known for every
> > functions and subfunctions. It is only to comparison purposes of the
> > numeric algorithms. Is there a possibility?
> >
> > please answer in german if possible.

Es tut mir leid. Ich kann Deutsch nicht sprechen.

> a <- 1

If you make that assignment inside a function, it won't be known outside the funtion, so "a" is not really global here.

Global assignment
x <<- 5

BUT, be aware of these cautions about the use of global variables:

"I wish <<- had never been invented, as it makes an esoteric and dangerous feature of the language *seem* normal and reasonable. If you want to dumb down R/S into a macro language, this is the operator for you." -- Bill.Venables, R-Help, July 30, 2001

#thomas (tlumley), R-Help, Jan 24, 2001
This is one of the acceptable uses of <<-, as shown in demo(scoping). <<- is useful for modifying a variable that you know exists in the enclosing environment. Most of the problems come from people trying to use it to modify things in a parent environment or in the global environment.

Also see Section 13.3 "Global Data" in "Code Complete 2" ( including:

- Common Problems with Global Data
- Use Global Data Only as a Last Resort
- How to Reduce the Risks of Using Global Data

efg mailing list PLEASE do read the posting guide! Received on Wed Jan 25 10:11:09 2006

This archive was generated by hypermail 2.1.8 : Wed 25 Jan 2006 - 14:08:01 EST