function rand ( n )
{
  return ( Math.floor ( Math.random ( ) * n + 1 ) );
}
  
// determins how many images to randomly select from for each publication
var pcs = 3;
var wfr = 2;
var pm  = 2;
var el  = 2;

var pubImageCount = 0;

// random images must be named: index_$pub_$n.jpg

function getRandImage( pub ) {
  switch (pub) {
   case 'pcs': pubImageCount = pcs;
   case 'wfr': pubImageCount = wfr;
   case 'pm' : pubImageCount = pm;
   case 'el' : pubImageCount = el;    
  }
  
  imageNum = rand(pubImageCount);
  imageName = "index_" + pub + "_" + imageNum + ".jpg";
  return imageName;
}