R help - Jul 2008 - Identifying common prefixes from a vector of words, and delete those prefixes

For example, c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.animal"). How can I identify the common prefix is
".is.an.animal" and delete it to give c("dog",
"cat", "rat") ?
 
Thanks
_________________________________________________________________


	[[alternative HTML version deleted]]

> For example, c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.
> animal"). How can I identify the common prefix is
".is.an.animal"
> and delete it to give c("dog", "cat", "rat")
?
foo <- c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.animal")
sub(".is.an.animal", "", foo)

Being pedantic, ".is.an.animal" is a suffix not a prefix since it
comes
afterwards.

Regards,
Richie.

Mathematical Sciences Unit
HSL


------------------------------------------------------------------------
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This message contains privileged and confidential inform...{{dropped:20}}

There MUST be a better way but this will work. 

x <- c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.animal")
bb <- strsplit(x, "\\.")
myfun <- function(m) m[1]
animals  <- unlist(lapply(bb, myfun))
animals




--- On Thu, 7/31/08, Daren Tan <daren76 at hotmail.com> wrote:
> From: Daren Tan <daren76 at hotmail.com>
> Subject: [R] Identifying common prefixes from a vector of words, and delete
those prefixes
> To: r-help at stat.math.ethz.ch
> Received: Thursday, July 31, 2008, 7:11 AM
> For example, c("dog.is.an.animal",
> "cat.is.an.animal", "rat.is.an.animal").
> How can I identify the common prefix is
> ".is.an.animal" and delete it to give
> c("dog", "cat", "rat") ?
>  
> Thanks
> _________________________________________________________________
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained,
> reproducible code.

      __________________________________________________________________
[[elided Yahoo spam]]

A more general solution:

strip.fun <- function(x, split=".") {
	xx <- strsplit(x, split, fixed=TRUE)
 	txx <- table(unlist(xx))
	nxx <- names(txx)[txx > 1]
	setdiff(unlist(xx), nxx)
}
> x <- c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.animal")
> strip.fun(x)
[1] "dog" "cat" "rat"
> y <- c("my_cat_pet", "my_dog_pet",
"my_rat_pet")
> strip.fun(y, "_") 
[1] "cat" "dog" "rat"


-Christos
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of John Kane
> Sent: Thursday, July 31, 2008 12:48 PM
> To: r-help at stat.math.ethz.ch; Daren Tan
> Subject: Re: [R] Identifying common prefixes from a vector of 
> words,and delete those prefixes
> 
> There MUST be a better way but this will work. 
> 
> x <- c("dog.is.an.animal", "cat.is.an.animal", 
> "rat.is.an.animal") bb <- strsplit(x, "\\.") myfun
<-
> function(m) m[1] animals  <- unlist(lapply(bb, myfun)) animals
> 
> 
> 
> 
> --- On Thu, 7/31/08, Daren Tan <daren76 at hotmail.com> wrote:
> 
> > From: Daren Tan <daren76 at hotmail.com>
> > Subject: [R] Identifying common prefixes from a vector of 
> words, and 
> > delete those prefixes
> > To: r-help at stat.math.ethz.ch
> > Received: Thursday, July 31, 2008, 7:11 AM For example, 
> > c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.animal").
> > How can I identify the common prefix is ".is.an.animal" and 
> delete it 
> > to give c("dog", "cat", "rat") ?
> >  
> > Thanks
> > _________________________________________________________________
> > 
> > 
> > 	[[alternative HTML version deleted]]
> > 
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> 
> 
>       
> __________________________________________________________________
> [[elided Yahoo spam]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
>

Daren Tan <daren76 at hotmail.com> writes:
> For example, c("dog.is.an.animal", "cat.is.an.animal",
> "rat.is.an.animal"). How can I identify the common prefix is
> ".is.an.animal" and delete it to give c("dog",
"cat", "rat") ?
The 'Rlibstree' package from omegahat is quite fun for this sort of
thing:
> install.packages('Rlibstree',
repos="http://www.omegahat.org/R")
[snip]
> library(Rlibstree)
> rstrings <- function(string) {
+     lapply(lapply(strsplit(string, ""), rev),
+            paste, collapse="")
+ }
> pets <- c("dog.is.an.animal", "cat.is.an.animal",
"rat.is.an.animal")
> commonSfx <- rstrings(getCommonPrefix(rstrings(pets)))
> commonSfx
[[1]]
[1] ".is.an.animal"
> sub(commonSfx, "", pets)
[1] "dog" "cat" "rat"

Martin
  
> Thanks
> _________________________________________________________________
>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
-- 
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109

Location: Arnold Building M2 B169
Phone: (206) 667-2793