4 ms·
You may be right...I spent a lot of time thinking about that, and I convinced myself that this was correct, but I could be wrong. My thinking is that rand(N) in
by timr 12y ago
You may be right...I spent a lot of time thinking about that, and I convinced myself that this was correct, but I could be wrong. My thinking is that rand(N) in ruby returns a value from [0, N-1] inclusive, which is the complete index range of the sampled stream so far.
That sounded right to me. I could be convinced otherwise.
- danieldk 12y agoYou are not taking the index of the element that you are currently sampling into consideration. Suppose that the sample size is 1 and you are getting the second item (index 1). You will call rand(1), which has 0 as the only possible outcome. So, you will always replace the first item (index 0). Whereas if you would call rand(2) (possible outcomes: 0 and 1), you replace the item in the sample with probability .5 (assuming that the random number generator is uniform).
- timr 12y agoD'oh. Yes, I think you're right. That'll teach me to try to mentally debug code at 2AM! I'll fix the code and publish a new gem a bit later today. Thanks!