[R] apply for nested lists
Alexandre Sanchez Pla
asanchez at ub.edu
Wed Jan 26 17:49:58 CET 2005
Hi,
I am working with lists whose terms are lists whose terms are lists. Although
the real ones contain locuslink identifiers and GO annotations (I work with the
Bioconductor GO) package, I have prepared an simplified example of what I have
and what I would like to do with it:
Imagine I have a list such as:
tst.list<-list("1"=list("1A"=list(ID="1A",VAL=172),"1B"=list
(ID="1B",VAL=134),"1C"=list(ID="1C",VAL=0)),"2"=list("2A"=NA),"3"=list("3A"=list
(ID="3A",VAL=33),"3B"=list(ID="3B",VAL=2)))
I would like, for instance, to be able to extract some values such as the
content of the "VAL" field, which may sometimes not be available.
I may do it using a nested for such as:
x<-character(0)
for (i in 1:length(tst.list)){
if (!is.na(tst.list[[i]][[1]][[1]])){
for (j in 1:length(tst.list[[i]]))
{x<-c(x,tst.list[[i]][[j]]$VAL)}}
else
{x<-c(x, NA)}}
which gives me what I need
> x
[1] "172" "134" "0" NA "33" "2"
According to most R documents this may be done more efficiently using apply
instructions, but I have failed in my temptatives to obtain the same
Thanks for any help.
Alex
--
Dr.Alex Sánchez
Departament d'Estadística.
Universitat de Barcelona
asanchez at ub.edu
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