ntial.length-1].sort( (a,b) => b['确诊人数'] - a['确诊人数'] );
            
            keys = sortedforkey.map(d => d[keyHint]);
            keys = keys.filter(d => {return d !== alone});
            keys_hubei = Array.from(new Set(data_hubei.map( datum => datum[keyHint])));
            // generate low_max and up_max for Y-scale; 
            up_max = d3.max(sequential, seq => {
                result = 0;
                seq.forEach(s => {
                    if(s[keyHint] !== alone){
           