Galichon Enterprises - Example of Random Banners with specified distribution

<HEAD>

<!-- Begin
function banner(imgSource,url,alt,chance) {
   this.imgSource = imgSource;
   this.url = url;
   this.alt = alt;
   this.chance = chance;
}
function dispBanner() {
   with (this) document.write("<A HREF=" + url + "><IMG SRC='" + imgSource + "' WIDTH=468 HEIGHT=60 BORDER=0 ALT='" + alt + "'></A>");
}
banner.prototype.dispBanner = dispBanner;
banners = new Array();

banners[0] = new banner("images/banner/galichon_logo.jpg",
                        "http://www.galichon.net target='_blank'",
                        "Galichon Enterprises - Certified Cool",
                        10);
banners[1] = new banner("http://images.paypal.com/images/lgo/logo1.gif",
                        "https://secure.paypal.com/affil/pal=rich%40galichon.net target='_blank'",
                        "Make payments with PayPal - its fast, free and secure!", 
                        14);
banners[2] = new banner("http://www.galichon.net/images/banner/better_banner.jpg",
                        "http://setiathome.berkeley.edu target='_blank'",
                        "Join Seti@Home", 
                        12);
////////////////////////////////////////////////////////////////////////////////////////////
// A D D   M O R E   B A N N E R S   H E R E
//
// banners[x] = new banner(<banner source image>,
//                         <url to link to when the banner is clicked>,
//                         <alt>,
//                         <the chance this banner has in which to be randomly selected>);
//
// Please feel free to modify banners[1] and up.  You may further customize this script by
// adding more banners, too.  Just be sure to increment the banners array by 1 for each new
// banner.  Also, remember to adjust the chance property for each banner to get the
// banner distribution you desire.  No other modifications to this script are necessary for
// it to work on your site.
//
// To increase the chance of a banner being randomly selected, increase it's corresponding
// 'chance' property relative to the other banners.
//
// Example: a banner with chance=20 is 2 times more likely to be chosen over a banner
// with chance=10.  Furthermore, a banner with chance=60 is 3 times more likely to be
// chosen over the banner with chance=20 and 6 times more likely to be chosen over the
// banner with chance=10.
//
// Another example: if there are 3 banners, each of which having chance=10, then they would
// each have an equal chance of being selected.
//
// Note: it is not necessary for the "sum of all chances" to add up to 100.  The sum
// produced is arbitrary.  Rather, it's the ratios of each banner's "chance" divided by the
// "sum of all chances" which ultimately determines the banner distribution.
//
// Recommendation: the minimum chance a given banner should have is 10.  Lower numbers than
// this have caused skewed results from the Math.random function.  That is to say, instead
// of selecting chances of 1, 2, and 3, use 10, 20, and 30 respectively.
//
// Enjoy! - Rich Galichon
////////////////////////////////////////////////////////////////////////////////////////////
sum_of_all_chances = 0;
for (i = 0; i < banners.length; i++) {
  sum_of_all_chances += banners[i].chance;
}
function randomBanner() {
  chance_limit = 0;
  randomly_selected_chance = Math.round((sum_of_all_chances - 1) * Math.random()) + 1;
  for (i = 0; i < banners.length; i++) {
    chance_limit += banners[i].chance;
    if (randomly_selected_chance <= chance_limit) {
      document.write("<A HREF=" + banners[i].url + "><IMG SRC='" + banners[i].imgSource + "' WIDTH=468 HEIGHT=60 BORDER=0 ALT='" + banners[i].alt + "'></A>");
      return banners[i];
      break;
    }
  }
}
//  End -->
</SCRIPT>

</HEAD>

<BODY>

</script>

Did you use this script? Do you like this site? Please link to us!

This banner was selected by the Dynamic Banner Distribution routine.

The following banners are all banners we currently display across our site through use of our Dynamic Banner Distribution routine.