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luke
2007 Apr 18
2
Computing an ordering on subsets of a data frame
If I have a data frame X that looks like this:
A B
- -
1 2
1 3
1 4
2 3
2 1
2 1
3 2
3 1
3 3
and I want to make another column which has the rank of B computed
separately for each value of A.
I.e. something like:
A B C
- - -
1 2 1
1 3 2
1 4 3
2 3 3
2 1 1
2 1 2
3 2 2
3 1 1
3 3 3
by(X, X[,1], function(x) { rank(x[,1], ties.method="random") } ) almost
seems to work, but the data is not