function siz=weigth2size(weigth)
% the size of the points is calculated from the weigth value 

if and(weigth >=0.0,weigth < 0.10) 
    siz=1;
else
    if and(weigth >=0.10,weigth < 0.25)
      siz=4;
    else
      if and(weigth >=0.25,weigth < 0.50)
          siz=6;
      else
          if and(weigth >= 0.50, weigth <0.75) 
           siz=8;
          else
              if(weigth > 0.75)
                 siz=10;
             end;
          end;
      end;
    end;
end;