code: function _fnVisibleToColumnIndex( oSettings, iMatch )
  		{
  			var iColumn = -1;
  			
  			for ( var i=0 ; i<oSettings.aoColumns.length ; i++ )
  			{
  				if ( oSettings.aoColumns[i].bVisible === true )
  				{
  					iColumn++;
  				}
  				
  				if ( iColumn == iMatch )
  				{
  					return i;
  				}
  			}
  			
  			return null;
  		}
docs: Covert the index of a visible column to the index in the data array (take account
  of hidden columns)
  @param {object} oSettings dataTables settings object
  @param {int} iMatch Visible column index to lookup
  @returns {int} i the data index
  @memberof DataTable#oApi