Are your for loops too slow in R ? Are loops that should take seconds actually taking hours ?
As I found out recently, how you structure your code can make a huge difference in execution times. Fortunately making a few small changes to your code can speed up these loops by several orders of magnitude.
This Stack Overflow post goes through a number of ways to optimise your for loops – I only implemented the first method and my loop run time went from over an hour to less than 10 seconds !!!
The secret ? to loop over a vector rather than data frames as R is optimised for vector and matrix operations.