Questions about set.seed() in R

Question

I understand what set.seed() does and when I might use it, but I still have many questions about the function. Here are a few:

1. Is it possible to \

Answer 1

It's possible, if you set the seed to something like the final digits of your time epoch, but it's really not necessary. The intended use of PRNGs is that you set the seed once at the start of a session, and use successive generated variates from this. Do things differently, and you don't get to enjoy the various good theoretical and empirical properties the R RNGs have.

But I'm not sure you really understand the purpose of set.seed. It's not really there for you to get 'more random' numbers. If you are doing some kind of application for which the R PRNG is insufficient (for instance, if you require cryptographic randomness), you might as well generate all your random numbers by some alternate method and use them directly. The real purpose of set.seed is to produce reproducibility in results using RNGs. If you start the same analysis using the same sequence of random number generations, and set the seed to the same value, you will always get the same result. This is helpful in debugging, and for others reviewing your results.

To use the epoch time, do something like

t <- as.numeric(Sys.time())
seed <- 1e8 * (t - floor(t))
set.seed(seed); print(seed)