use c3 for stacked spline

server/lib/data_helper.js

@@ -0,0 +1,27 @@
+import cheerio from 'cheerio';
+import fs from 'fs';
+import moment from 'moment';
+
+class DataHelper {
+
+  static baseIrradiance(){
+    return new Promise((fnResolve, fnReject)=>{
+      fs.readFile(__dirname + '/../data/irradiance.html', (err, data)=>{
+        if (err) return fnReject(err);
+        var $ = cheerio.load(data),
+          base_irradiance = {};
+        $('tbody tr').each((i, elem)=>{
+          if (i === 0) return true;
+          var cells = $(elem).find('td'),
+            date_s = moment($(cells[1]).text(), 'YYYY-MM-DD').format('MM-DD'),
+            irradiance = parseFloat($(cells[2]).text());
+          base_irradiance[date_s] = irradiance;
+        });
+        fnResolve(base_irradiance);
+      });
+    });
+  }
+
+}
+
+export default DataHelper;