[R] counting row repetitions without loop
Waterman, DG (David)
david.waterman at diamond.ac.uk
Wed Feb 6 15:08:16 CET 2008
I have a data frame consisting of coordinates on a 10*10 grid, i.e.
1 4 5
2 6 7
3 6 6
4 7 5
5 5 7
6 6 7
7 4 5
8 6 7
9 7 6
10 5 6
What I would like to do is return an 10*10 matrix consisting of counts
at each position, so in the above example I would have a matrix where,
for example, cell [4,5] contains 2 and [6,7] contains 3. At the moment I
have implemented this using a for loop over the rows of the data frame,
however the data frames I want to process are very long so the loop
takes many minutes to complete. Can I do this in a more efficient way?
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