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

[David Winsemius]

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.
>
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David Winsemius, MD
West Hartford, CT