Hello,
Try this:
list1<-list(
"text, text, 2001, text",
"text, 2000, text",
"1999, text, text, text")
l1<-lapply(list1,function(x) gsub("\\D","",x))
[[1]]
[1] "2001"
[[2]]
[1] "2000"
[[3]]
[1] "1999"
unlist(l1)
[1] "2001" "2000" "1999"
A.K.
----- Original Message -----
From: jimi adams <[email protected]>
To: [email protected]
Cc:
Sent: Tuesday, July 31, 2012 11:33 AM
Subject: [R] year extraction over a list
Hello,
I have a data frame, one element in that data frame is a LIST, with each
element being a character string. I am trying to extract the first year listed
in each of those character strings. The character elements are typically csv,
but the position of the year can vary (think citations with varying citation
standards). I.e.,
foo$a
[[1]]
[1] text, text, 2001, text
[2] text, 2000, text
[3] 1999, text, text, text, …
I'm trying to figure out how to create a new list such that each element is
that year, i.e., the result on the above would be:
foo$year
[[1]]
[1] 2001
[2] 2000
[3] 1999
…
For some reason i'm not figuring out how to properly get lapply and strsplit
(or other alternatives) to play nicely together. Any help greatly appreciated.
thanks,
jimi
jimi adams
Assistant Professor
Department of Sociology
American University
e: [email protected]
w: jimiadams.com
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
