On Feb 24, 2010, at 8:18 PM, Jon Erik Ween wrote:
Friends
I can't quite find a direct answer to this question from the lists,
so here goes:
I have several dataframes, 200+ columns 2000+ rows. I wish to script
some operations to perform on some of the variables (columns) in the
data frames not knowing what the column number is, hence have to
refer by name. I have variable names in a text file "varlist". So,
something like this:
for (i in 1:length(varlist)){
j<-varlist[i]
v<-mean(Dataset[[j]])
print(v)
}
Without a data example this is untested guesswork and may fail if
varlist is not a vector or something that can be coerced to a vector.
Might help to look at str(varlist), ... anyway ...
for (i in varlist){
v<-mean(Dataset[ , i])
print(v)
}
If it doesn't work, then pay close attention to the error messages.
--
David
Now, if I force it
j<-"Var1"
v<-mean(Dataset[[j]])
print(v)
then it works, but not if i read the varlist as above.
Looking at "j" I get:
print(j)
V1
1 Var1
Right. You are supplying a list as an index.
Hence there is a lot of other stuff read into "j" that confuses
"mean".
I think it is confusing "[[", but it's really more guesswork because
you did not supply a reproducible example.
I can't figure out how to just get the value of the variable and
nothing else. I've tried space separated, comma separated, tab
separated lists and all give the same error. I've tried get(),
parse()... no go.
Any suggestions?
Thanks a lot
Jon
Soli Deo Gloria
Jon Erik Ween, MD, MS
Scientist, Kunin-Lunenfeld Applied Research Unit
Director, Stroke Clinic, Brain Health Clinic, Baycrest Centre
Assistant Professor, Dept. of Medicine, Div. of Neurology
University of Toronto Faculty of Medicine
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Baycrest Centre
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Toronto, Ontario M6A 2E1
Canada
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Email: jw...@klaru-baycrest.on.ca
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