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List filtration

4 messages · Dimitris Rizopoulos, Rajarshi Guha, Johannes Graumann

Original
Johannes Graumann
# 
Hello R-ologists,

Imagine you have a list "list" like so:
[[1]]
[1] "IPI00776145.1" "IPI00776187.1"

[[2]]
[1] "Something" "IPI00807764.1" "IPI00807887.1"

[[3]]
[1] "IPI00807764.1"

[[4]]
[1] "Somethingelse"

What I need to achieve is a filtered list "list2" like so:
[[1]]
[1] "IPI00776145.1"

[[2]]
[1] "IPI00807764.1"

[[3]]
[1] "IPI00807764.1"

So: 
- if sublist-entry 1 start with "^IPI" make it the list-entry.
- otherwise chose the first "^IPI" sublist-entry present.
- delete the list-entry if not "^IPI" sublist-entry present.

Can anybody nudge me towards an elegant solution without looping - I have
LOTS of entries to process ...

Thanks for your Teachings,

Joh
Dimitris Rizopoulos
# 
try this:

lis. <- lapply(lis, function(x) if (length(ind <- grep("^IPI", x))) 
x[ind[1]] else NULL)
lis.[!sapply(lis., is.null)]


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Johannes Graumann" <johannes_graumann at web.de>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, February 22, 2007 3:33 PM
Subject: [R] List filtration
Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
Rajarshi Guha
#
On Thu, 2007-02-22 at 15:33 +0100, Johannes Graumann wrote:
[snip]
One way to do it would be:

l <- list(c("IPI00776145.1", "IPI00776187.1"),
          c("Something", "IPI00807764.1", "IPI00807887.1"),
          c("IPI00807764.1"),
          c("Somethingelse"))

f <- function(x) {
  r <- grep("^IPI", x, value=TRUE)
  if (length(r) > 0) return(r[1])
  else return(NA)
}

l2 <- unlist(lapply(l, f))
l2 <- l2[!is.na(l2)]

But I'm sure that more elegant solutions will be posted

-------------------------------------------------------------------
Rajarshi Guha <rguha at indiana.edu>
GPG Fingerprint: 0CCA 8EE2 2EEB 25E2 AB04 06F7 1BB9 E634 9B87 56EE
-------------------------------------------------------------------
Writing software is more fun than working.
Johannes Graumann
# 
Thanks for your help!

Joh
Dimitris Rizopoulos wrote: