weights and probability

[renny]

Hello,

I have a table with rows of text, etc. I would like to give each row a weight (e.g. 0.5 or 1 or etc). And the more weights the row have, the more often will that row be chosen to be displayed.

How do I go about doing this? Please help me. Any advice or suggestions are much appreciated.

Thanks,
Renny

[barand]

First, make your weights relative whole numbers. (1 and 2 instead of 0.5 and 1).

Read your table and, for each record, write the text into an array. The number of times you add it to the array will be governed by the weight value.

Do a random selection from the array.

$textarray = array();
$res = mysql_query("select `text`, weight from mytable");
while (list($txt, $wt) = mysql_fetch_row($res)) {
   for ($i=0; $i < $wt; $i++) 
       $textarray[] = $txt;
}

$key = array_rand($textarray);
echo $textarray[$key];

hth

[Sxooter]

In PostgrseSQL:

create table test (info text, weight int);
insert into test values ('abc',1);
insert into test values ('DEF,2);
insert into test values ('xyz',4);
select from test order by random()weight;

tada, you're done.

I think in MySQL the only change is to make random() into rand()

The advantage here is the database does all the work for you, and if you want to, you can assign weight to a float or numeric and not have to use just integers.

[csn]

ooooohhh weights suck 😉. check out how some of the other apps do it - like phpadsnew. Some populate arrays, others make probablity tables (i.e. one row in a db table for each chance of getting seleted). I think phpadsnew runs a cron script to recompute probabilities.