[R] Regular Expressionsionism

[jasont@indigoindustrial.co.nz]

> "Derek Eder" <Derek.Eder at neuro.gu.se> writes:
..
> > ... Using a regular expression in the "pattern" argument to 
> > list.files() to restrict the return to filenames which
> > contain both "Elstim" and "post".  E.g.,
> > 
> > >list.files()
> > ... 
> > [133] "J30710_Control_msa_amplitude_5_25_s1-
30w.pre"                                    
               
> > [134] "J30710_Elstim_msa_amplitude_5_25_s1-
30w.post"                                    
               
> > [135] "J30710_Elstim_msa_amplitude_5_25_s1-
30w.pre"                                     
               
> > [136] "J30712_Control_msa_amplitude_5_25_s1-41_44-
46_48w.post"                          
               
> > [137] "J30712_Control_msa_amplitude_5_25_s1-41_44-
46_48w.pre"                           
               
> > [138] "J30712_Elstim_msa_amplitude_5_25_s1-17_19-
43_45_48w.post"                        
               
> >                                        
> > I have not found the key to generating the logical AND equivalent of 
the "|" OR infix
operator, a 
> > proxy for the simpleton's dream:  my.list.files(pattern="*Elstim" 
& "*post") 

In this case, the quick and (very) dirty method I'd also use is:

grep("Elstim",grep("post",list.files()))

generalising that via recursion to match an arbitrary number of REs 
and "&" and "|" operators is left as an excercise.... 

Cheers

Jason

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