Identify Objects that end with .f (and all caps)

Dear R Helpers,

I am trying to find a way to identify all the objects in my  
environment
that are all caps and then end with .f.  I can do the all caps part  
pretty
easily, but I have tried a number of variations on the \ and can't  
get a
recognition of that operator.  As a simple example

A.f<-"foo1"
AA.f<-"foo2"
aa.f<-"foo3"
A.a<-"foo4"
ls()
[1] "A.a"  "A.f"  "aa.f" "AA.f"
temp1<-ls(pattern="[A-Z]")
temp1
[1] "A.a"  "A.f"  "AA.f"

temp2<-ls(pattern=\f)

Error: unexpected input in "temp2<-ls(pattern=\"

The end goal is to isolate A.f and AA.f and not the others.
In terms of just getting the 'ending with .f' portion, I have tried a
number of variations in the pattern=\f, but can't get R to recognize  
what
I want.

Your guidance would be much appreciated.
--John J. Sparks, Ph.D.

On May 14, 2011, at 3:38 PM, Sparks, John James wrote:

Dear R Helpers,

I am trying to find a way to identify all the objects in my  
environment
that are all caps and then end with .f.  I can do the all caps part  
pretty
easily, but I have tried a number of variations on the \ and can't  
get a
recognition of that operator.  As a simple example

A.f<-"foo1"
AA.f<-"foo2"
aa.f<-"foo3"
A.a<-"foo4"
ls()
[1] "A.a"  "A.f"  "aa.f" "AA.f"
temp1<-ls(pattern="[A-Z]")
temp1
[1] "A.a"  "A.f"  "AA.f"

temp2<-ls(pattern=\f)

Error: unexpected input in "temp2<-ls(pattern=\"

You need to double the '\':

temp1<-ls(pattern="[A-Z]\\.f")

temp1

[1] "A.f"      "AA.f"     "NYSE.A.f"

The end goal is to isolate A.f and AA.f and not the others.
In terms of just getting the 'ending with .f' portion, I have tried a
number of variations in the pattern=\f, but can't get R to  
recognize what
I want.

Your guidance would be much appreciated.
--John J. Sparks, Ph.D.

David Winsemius, MD
West Hartford, CT