How about:
l <- list("")
l[[1]] <- c("A1","A2","A3")
l[[2]] <- c("B1","B2","B3")
l[[3]] <- c("C1","B2","B3")
lapply(l, "[[", 2)
or
sapply(l, "[[", 2)
I hope it helps.
Best,
Dimitris
On 2/14/2012 2:44 PM, geotheory wrote:
Basic question (if you know the answer)... I am dealing with a list of
commonly-formatted sub-lists, for example:
l<- list("")
l[[1]]<- c("A1","A2","A3")
l[[2]]<- c("B1","B2","B3")
l[[3]]<- c("C1","B2","B3")
Lets say I need to extract every 2nd item (i.e. A2, B2, C2). [[]] cannot be
used. l[2] returns practically the same as l[[2]]. Is there a way to
achieve this without having to loop or convert to data.frame?
Thanks in advance.
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--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/
______________________________________________
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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.
