Probability of a Random Number

Dudaa

I'll explain what I'm doing first as I don't know the mathematical term.

I want to pick topics at random from a forum database but I want it to concentrate on picking the newest posts first. Basically I'll have order by latest posts and want the most recent topics returned more often than topics that are a year or two old.

Now doing something like

$num = (time() & 1) ? mt_rand(1, 10) : mt_rand(1, mt_rand(10, 1000));

this will give make the numbers 1 - 10 appear more than 10 - 1000 but a number like 134 has the same probability as 857 which isn't ideal.

If a forum has 100k topics it's not much use. I want 1 to have a greater change of appearing than 2 which would be greater than 3 which would be greater than 4 ....etc.

It's to be used on a script that adds a reply to the topics so I want it to be natural and add replies randomly to the most recent topics and only occasionally bump old topics sorta like the way a real forum works.

I don't mind if I get one number per run but ideally I'd have say 10 so I could run a loop on say 10 topics at a time.

I hope you understand what I'm trying to accomplish. Anyone have any ideas or suggestions on how best to do this?

NogDog

One way is to generate multiple random numbers and choose the one closest to the "end" you want to favor. For instance, if we assume that the latest posts will have the highest ID number:

$id = max(mt_rand($min, $max), mt_rand($min, $max));

To weight it more heavily, add more values to the max() or min():

$id = max(mt_rand($min, $max), mt_rand($min, $max), mt_rand($min, $max));

laserlight

Dudaa wrote:
It's to be used on a script that adds a reply to the topics so I want it to be natural and add replies randomly to the most recent topics and only occasionally bump old topics sorta like the way a real forum works.

With all due respect, this sounds a little fishy. Why do you want to do this?

Dudaa

laserlight;10956998 wrote:
With all due respect, this sounds a little fishy. Why do you want to do this?

Good question and fair point. A friend has a Graphics Tutorials forum with and has created a lot of tutorials as well as other Photoshop tips. The problem is the whole forum is rather dead from an activity point. He wants a few replies to topics in the tutorials section to make the site more active looking and welcoming to new potential members. Currently people view the tutorials but don't reply.

A message is picked at random from an array and added to topic as a reply. Their all basic messages like "thanks you for this. I've used it in a project I'm working on now", "Great tutorial mate, keep up the good work." etc etc.

It's purely a marketing thing as new members find it a lot easier to reply to topics when one or two people have already commented. People are more timid and shy to be the first.

I suppose morally it's not that nice but it's not harming anyone. I apologizes to anyone who has a problem with it morally but I'm being honest. I could have made up some other random fake reason.

NogDog;10956996 wrote:
One way is to generate multiple random numbers and choose the one closest to the "end" you want to favor. For instance, if we assume that the latest posts will have the highest ID number:
$id = max(mt_rand($min, $max), mt_rand($min, $max));
To weight it more heavily, add more values to the max() or min():
$id = max(mt_rand($min, $max), mt_rand($min, $max), mt_rand($min, $max));

Thanks for this NogDog. It's another way I was looking at it and does work as the site's not that big but it's still not exactly weighted is a step by step process. I've still no idea how to do it step by step to achieve a more accurate distribution of replies. Perhaps a matrix or something but not sure.

Thanks for your suggestion though and this will do for now.

dagon

wow fake posts to a forum, sure why to make users welcome.:rolleyes: