_Genetic_Code = {
                     {14,13,14,13,7,7,7,7,19, 5,19, 5,2,2,3,2,
                      12,11,12,11,6,6,6,6,19,19,19,19,1,1,1,1,
                      16,15,16,15,8,8,8,8,20,20,20,20,4,4,4,4,
                      10,9, 10,9, 5,5,5,5,10,17,18,17,1,0,1,0}
                      
/* -------------------------------------------------------------------------- */
/* Builds a vector of codon frequencies by multiplying observed frequencies   */
/* -------------------------------------------------------------------------- */

function BuildCodonFrequencies (obsF)
{
        PIStop = 1.0;
        result = {61,1};
        hshift = 0;

        for (h=0; h<64; h=h+1)
        {
                first = h$16;
                second = h%16$4;
                third = h%4;
                if (_Genetic_Code[h]==10) 
                {
                        hshift = hshift+1;
                        PIStop = PIStop+obsF[first][0]*obsF[second][1]*obsF[third][2];
                        continue; 
                }
                result[h-hshift][0]=obsF[first][0]*obsF[second][1]*obsF[third][2];
                
        }
        return result*(1.0/(PIStop))
        
}