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scoping problem?

3 messages · yudi@hermes.ucd.ie, Thomas Lumley, Peter Dalgaard

yudi@hermes.ucd.ie
# 
Dear R-helpers: (this is part of a bigger program)
the following fails as a function, but runs OK 
if we comment out the  fnfn_ function()  line.
Any hint would be appreciated.  -Yudi-

R : Copyright 1998, The R Development Core Team
Version 0.63.0 Beta (Nov 13, 1998) -- on WIndows3.11

fnfn _ function (m=10,n=10,spar=2)
{
fn _ function(u,v){
     uc_ u-floor(m/2)-1
     vc_ v-floor(n/2)-1
     exp(-(uc^2 + vc^2)/2/spar^2)
     }
 x1_ 1:m ; x2_ 1:n
 x12 _ outer(x1,x2,FUN='fn')
 filt _ x12/sum(x12)
 image(filt)
}
Error in get(x, envir, mode, inherits) : variable "fn" was not found

------------------------------
Yudi Pawitan: yudi at ucd.ie
Department of Statistics, UCD
Dublin 4, Ireland
Ph : 353-1-706 7641
Fax: 353-1-706 1186
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Thomas Lumley
#
On Thu, 21 Jan 1999 yudi at hermes.ucd.ie wrote:

            

      
      
      
    

        
In both an old and the current development release you can fix this by
removing the quotes around 'fn', or by using FUN=get("fn",mode="function")

The problem is in outer(), in either the original or the current improved
version. If FUN is a string we use get(FUN,mode="function"), which looks
for FUN in the current environment and all parent environments. The
problem is that "current" here means the environment in outer() or in
match.fun(), not the environment outer() was called from. 

We probably need to fix match.fun() to take an environment parameter and
outer() to then use match.fun(FUN,env=sys.frame(sys.parent()))


Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle.





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      Peter Dalgaard
    

    

      
      #
    

  


  

      
yudi at hermes.ucd.ie writes:

            

      
      
      
    

        
You want to get rid of the quotes around fn in the outer() call. If
you pass a text string rather than the actual function, outer() will
go looking for a function of that name in its own lexical scope and fail.