data frame has 2 columns, 20 years of portfolio returns, and 20 years of % withdrawn.
using a starting portfolio value, calculate the 20 ending portfolio values for each year and the dollar amount withdrawn.
worked ok looping through the data frame, but was unreasonably slow.
never figured out how to use a vectorized method that could go through the frame building each new element from the one previously calculated.
maybe I missed something obvious?
(the parallel part came in because I was doing it on a lot of portfolios, so to speed it up just launched the same slow function on several lists of them in parallel. writing that one function above in C probably would have been OK. I think I got it to work but then I couldn't get the right version of compiler to work with the right version of R which supported the other libraries I was using. was a few years ago so maybe things weren't as stable. I never said I was very good :)
I agree about 3 OO systems, but let's not mix things up here. Casual user (who doesn't know sapply) doesn't interact with that.