function _fnFilterColumn ( settings, searchStr, colIdx, regex, smart, caseInsensitive )
	{
		if ( searchStr === '' ) {
			return;
		}
	
		var data;
		var out = [];
		var display = settings.aiDisplay;
		var rpSearch = _fnFilterCreateSearch( searchStr, regex, smart, caseInsensitive );
	
		for ( var i=0 ; i<display.length ; i++ ) {
			data = settings.aoData[ display[i] ]._aFilterData[ colIdx ];
	
			if ( rpSearch.test( data ) ) {
				out.push( display[i] );
			}
		}
	
		settings.aiDisplay = out;
	}
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