[R] regexpr and portability issue

[Gabor Grothendieck]

Try this.  The regular expression says to match 
- anything 
- followed by a double underscore 
- followed by one or more digits
- followed by an underscore 
- followed by anything.  
The digits have been parenthesized so that they can be referred to in
the backreference "\\1".    Also use the R function dirname
rather than regular expressions.

base.name <- sub(".*__([[:digit:]]+)_.*", "\\1", aFileName, ext = TRUE)
base.dir <- dirname(aFileName)


On 8/3/05, Marco Blanchette <mblanche at uclink.berkeley.edu> wrote:
> Dear all--
> 
> I am still forging my first arms with R and I am fighting with regexpr() as
> well as portability between unix and windoz. I need to extract barcodes from
> filenames (which are located between a double and single underscore) as well
> as the directory where the filename is residing. Here is the solution I came
> to:
> 
> aFileName <-
> "/Users/marco/Desktop/diagnosticAnalysis/test/MA__251329410021_S01_A01.txt"
> t <- regexpr("__\\d*_",aFileName, perl=T)
> t.dir <- regexpr("^.*/", aFileName, perl=T)
> base.name <- substr(aFileName, t+2, t-2 + attr(t,"match.length"))
> base.dir <- substr(aFileName, t.dir, attr(t.dir,"match.length"))
> 
> My questions are:
> 1) Is there a more elegant way to deal with regular expressions (read here:
> more easier, more like perl style).
> 2) I have a portability problem when I extract the base.dir Windoz is using
> '\' instead of '/' to separate directories.
> 
> Any suggestions/comments
> 
> Many Tx
> 
> Marco Blanchette, Ph.D.
> 
> mblanche at uclink.berkeley.edu
> 
> Donald C. Rio's lab
> Department of Molecular and Cell Biology
> 16 Barker Hall
> University of California
> Berkeley, CA 94720-3204
> 
> Tel: (510) 642-1084
> Cell: (510) 847-0996
> Fax: (510) 642-6062
> 
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