Pivot Table Value Difference

var columns = 3;
var avg = 0;
var val = '';
var temp=0;
var title = "text";

widget.on('ready', function(se, ev){
 var grand_total = $("span:contains('Grand Total')");
 grand_total.text(title);
 
  $.each($("tbody tr"), function(){
  var num = $("tbody tr:first").children().length - columns;
  var e = element;
  var w = widget;
  var d = dashboard;
 var cell = $(this).children().last();


 for (var a = 0; a < num; a++){
    cell = cell.prev();

    if (avg == 0) {//debugger;
 //console.log(cell.children().text());
 if (cell.children().text() == " ") {//debugger;
 temp = 0;
 avg = 0;
 }
 else {
  temp = parseFloat(cell.attr("val"));
 avg = parseFloat(cell.attr("val"));
 }
 }
  else {
 if (cell.children().text() == " ") {
 avg = 0 - temp;
 }
 else {
    avg = parseFloat(cell.attr("val"))-temp;
 }
  }
 }
 cell = $(this).children().last();
 cell.children().text(avg.toString().substring(0,8));
avg = 0;
temp = 0;
  }); 
});