paste together object names to pass it on to a function
This should do it: ?"[["
gnuff<-list()
gnuff$IHD$LE<-66
gnuff$LUNG$LE <-55
nam <- c("LUNG","IHD")
x <- numeric(2) # allocate
for(i in 1:2)
+ x[i] <- gnuff[[nam[i]]]$LE / 2
x
[1] 27.5 33.0 On Fri, Jan 30, 2009 at 12:06 PM, stefan.duke at gmail.com
<stefan.duke at gmail.com> wrote:
Hello,
I have a maybe trivial question, but I simply don't understand well
enought how to work with text/strings:
I have a rather compelx data structure, a big list with several
sub-lists/dataframes and for certain calculations (which I do in
loops), I only need a certain group of sub-lists/dataframes, which I
want to specify with a name vector and paste together the object name
and pass it on to a function.
Here an (hopefully) instructive example
#Data Example
gnuff<-list()
gnuff$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
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