On Tue, 23 Dec 2008, Sean Zhang wrote:
Dear R-Helpers:
I am a entry level user of R.
You need to read
An Introduction to R
particularly this section:
2.7 Index vectors; selecting and modifying subsets of a data set
...
2. A vector of positive integral quantities
Also, see
?Subscript
and run
example( Subscript )
HTH,
Chuck
Have the following question. Many thanks in advance.
# value.vec stores values
value.vec <- c('a','b','c')
# which.vec stores the locations/indexs of values in value.vec.
which.vec <- c(3, 2, 2, 1)
# How can I obtain the following vector based on the value.vec and which.vec
mentioned above
# vector.I.want <- c('c', 'b', 'b', 'a')
# 3 2 2 1
# I try to avoid using the following loop to achieve the goal because the
which.vec in reality will be very long
vector.I.want <- rep(NA,length(which.vec))
for (i in 1:length(which.vec))
{ vector.I.want[i] <- value.vec[which.vec[i]] }
# is there a faster way than looping?
Thanks in advance.
-Sean
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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