Dear R-helpers,
I have a question about giving index.
Suppose that I have a vector say, id=1:5, and each of them have some given
index but some of them may share the same index
Now, I have another vector, and I want to give it a index based what just
defined.

# 5 subjects
test1=1:5
# corresponding index, so here, subject 2 and subject 4 share the common
index "1"
index=c(3,1,2,1,4)

# now I have another vector, and I want to use the index defined above
test2=c(5,4,2,1,1,5,3)

## so, the result  should be something like this--index of test2 is
(4,1,1,3,3,4,2)

How can I program this ?

Any help will be highly appreciated.

Thank you all,
Carrie

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