code: function _fnFilterColumn ( settings, searchStr, colIdx, regex, smart, caseInsensitive )
  	{
  		if ( searchStr === '' ) {
  			return;
  		}
  	
  		var data;
  		var display = settings.aiDisplay;
  		var rpSearch = _fnFilterCreateSearch( searchStr, regex, smart, caseInsensitive );
  	
  		for ( var i=display.length-1 ; i>=0 ; i-- ) {
  			data = settings.aoData[ display[i] ]._aFilterData[ colIdx ];
  	
  			if ( ! rpSearch.test( data ) ) {
  				display.splice( i, 1 );
  			}
  		}
  	}
docs: Filter the table on a per-column basis
  @param {object} oSettings dataTables settings object
  @param {string} sInput string to filter on
  @param {int} iColumn column to filter
  @param {bool} bRegex treat search string as a regular expression or not
  @param {bool} bSmart use smart filtering or not
  @param {bool} bCaseInsensitive Do case insenstive matching or not
  @memberof DataTable#oApi