paste together object names to pass it on to a function

Perhaps this will help:

#Data Example
gnuff<-list()
gnuff$IHD$LE<-66
gnuff$LUNG$LE <-55

#This is the list, where I collect data for different diseases at the
#second level of the list
#Now I want to do calcualtions just for these two diseases and the
#sub-list "LE" within these diseases

nam <- c("LUNG","IHD")

for(i in nam) print(gnuff[[i]])  # use the elements of nam as the index
values

# the lack of output from an evaluation done within the for-loop might be
one of Burns' Infernal examples.
# here's see one of my "mistakes":   for(i in nam) (gnuff[[i]])
#---returns a list---
#$LE
#[1] 55

#$LE
#[1] 66

#---
 for(i in nam) print(gnuff[[i]]$LE)  #use list extraction to get the values
#[1] 55
#[1] 66



On Jan 30, 2009, at 12:06 PM, stefan.duke at gmail.com wrote:

Hello,
I have a maybe trivial question, but I simply don't understand well
enought how to work with text/strings:

I have a rather compelx data structure, a big list with several
sub-lists/dataframes and for certain calculations  (which I do in
loops), I only need a certain group of  sub-lists/dataframes, which I
want to specify with a name vector and paste together the object name
and pass it on to a function.

Here an (hopefully) instructive example

#Data Example
gnuff<-list()
gnuff$IHD$LE<-66
gnuff$LUNG$LE <-55

#This is the list, where I collect data for different diseases at the
second level of the list
#Now I want to do calcualtions just for these two diseases and the
sub-list "LE" within these diseases


nam <- c("LUNG","IHD")

for(i in 1:2)
x[i] <- paste("gnuff",nam[i],"LE",sep="$") /2
x

#So I try to paste the name of the object which I mean
(gnuff$IHD$LEand gnuff$LUNG$LE, respectivly), but R treats them as a
string and not as the name of an object.
# I tried seveal commands to make it treat like an object name (the
get() looked most promising), but so far to no avail

#commands I have tried
j <- eval(paste("gnuff",nam[i],"LE",sep="$"))
parse(paste("gnuff",nam[i],sep="$"))
quote(paste("gnuff",nam[i],sep="$"))
get(paste("gnuff",nam[i],sep="$"))

Anybody any hints where to look?
Thanks and have a great weekend!
Best,
Stefan