R help - Jul 2009 - Warning when trying to access a variable out of scope?

Hi,

I was wondering if I could get R to warn me, or give me a rude  
awakening somehow, if I'm accessing a variable that is out of my  
function's scope.

For example, often times I'm creating a function as I'm testing it in  
the REPL, copying and pasting between both.

As a simple example, I might end up with a function like:

f <- function(a, b) {
   a + b.test
}

Where b.test was defined in my workspace as I'm mucking about in the  
REPL, but "clearly" I should have written:

f <- function(a,b) {
   a + b
}

I could go on for a while in my session w/o noticing the problem  
(since b.test is in my global env), and unbeknownst to me, my function  
will keep accessing the "b.test" variable when I really want it to  
work on the "b" var that I'm passing in to it.

Is there some setting or someway I can get R to warn me that "b.test"
is being accessed outside the scope of my function?

Thanks,
-steve

--
Steve Lianoglou
Graduate Student: Physiology, Biophysics and Systems Biology
Weill Medical College of Cornell University

Contact Info: http://cbio.mskcc.org/~lianos/contact

On 7/2/2009 2:17 PM, Steve Lianoglou wrote:
> Hi,
> 
> I was wondering if I could get R to warn me, or give me a rude  
> awakening somehow, if I'm accessing a variable that is out of my  
> function's scope.
> 
> For example, often times I'm creating a function as I'm testing it
in
> the REPL, copying and pasting between both.
> 
> As a simple example, I might end up with a function like:
> 
> f <- function(a, b) {
>    a + b.test
> }
> 
> Where b.test was defined in my workspace as I'm mucking about in the  
> REPL, but "clearly" I should have written:
> 
> f <- function(a,b) {
>    a + b
> }
> 
> I could go on for a while in my session w/o noticing the problem  
> (since b.test is in my global env), and unbeknownst to me, my function  
> will keep accessing the "b.test" variable when I really want it
to
> work on the "b" var that I'm passing in to it.
> 
> Is there some setting or someway I can get R to warn me that
"b.test"
> is being accessed outside the scope of my function?
Not really, but the codetools package can analyze your functions and 
tell you which ones do things like that.  For example,

 > f <- function(a, b) {
+    a + b.test
+ }
 > checkUsage(f)
<anonymous>: no visible binding for global variable ?b.test?

or

 > checkUsageEnv(globalenv())
f: no visible binding for global variable ?b.test?

This is normally used in the package test code, but you can use it on 
individual functions or environments if you want.

Duncan Murdoch

Does this do what you want?
> b.test <- 3
> 
> f <- function(a,b) {
+ a+b.test
+ }
> 
> f(10,20)
[1] 13
> 
> environment(f) <- baseenv()
> 
> f(10,20)
Error in f(10, 20) : object 'b.test' not found
> 
>

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Steve Lianoglou
> Sent: Thursday, July 02, 2009 12:17 PM
> To: R-help at r-project.org
> Subject: [R] Warning when trying to access a variable out of scope?
> 
> Hi,
> 
> I was wondering if I could get R to warn me, or give me a rude
> awakening somehow, if I'm accessing a variable that is out of my
> function's scope.
> 
> For example, often times I'm creating a function as I'm testing it
in
> the REPL, copying and pasting between both.
> 
> As a simple example, I might end up with a function like:
> 
> f <- function(a, b) {
>    a + b.test
> }
> 
> Where b.test was defined in my workspace as I'm mucking about in the
> REPL, but "clearly" I should have written:
> 
> f <- function(a,b) {
>    a + b
> }
> 
> I could go on for a while in my session w/o noticing the problem
> (since b.test is in my global env), and unbeknownst to me, my function
> will keep accessing the "b.test" variable when I really want it
to
> work on the "b" var that I'm passing in to it.
> 
> Is there some setting or someway I can get R to warn me that
"b.test"
> is being accessed outside the scope of my function?
> 
> Thanks,
> -steve
> 
> --
> Steve Lianoglou
> Graduate Student: Physiology, Biophysics and Systems Biology
> Weill Medical College of Cornell University
> 
> Contact Info: http://cbio.mskcc.org/~lianos/contact
> 
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