Make week2week more resilient to date selections

lib/report_plugins/weektoweek.js

@@ -99,7 +99,7 @@ weektoweek.report = function report_weektoweek(datastorage, sorteddaystoshow, op
   sorteddaystoshow.forEach( function eachDay(day) {
     var weekNum = Math.abs(moment(day + ' 00:00:00').diff(startDay, 'weeks'));
 
-    if (!weekstoshow.includes(weekNum)) {
+    if (typeof weekstoshow[weekNum] === 'undefined') {
       weekstoshow[weekNum] = [ ];
     }
 
@@ -114,9 +114,11 @@ weektoweek.report = function report_weektoweek(datastorage, sorteddaystoshow, op
 
   weekstoshow.forEach( function eachWeek(week) {
     var sgvData = [ ];
-    var currDay = 0;
+    var weekStart = moment(week[0] + ' 00:00:00');
 
     week.forEach( function eachDay(day) {
+      var dayNum = Math.abs(moment(day + ' 00:00:00').diff(weekStart, 'days'));
+
       datastorage[day].sgv.forEach ( function eachSgv(sgv) {
         var sgvDate = moment(sgv.date);
         var sgvWeekday = moment(sgv.date).day();
@@ -128,9 +130,9 @@ weektoweek.report = function report_weektoweek(datastorage, sorteddaystoshow, op
 
         sgvData.push( {
           'color': sgvColor
-          , 'date': moment(sgv.date).subtract(currDay, 'days').toDate()
+          , 'date': moment(sgv.date).subtract(dayNum, 'days').toDate()
           , 'filtered': sgv.filtered
-          , 'mills': sgv.mills - currDay * 24*60*60000
+          , 'mills': sgv.mills - dayNum * 24*60*60000
           , 'noise': sgv.noise
           , 'sgv': sgv.sgv
           , 'type': sgv.type
@@ -138,8 +140,6 @@ weektoweek.report = function report_weektoweek(datastorage, sorteddaystoshow, op
           , 'y': sgv.y
         });
       });
-
-      currDay += 1;
     });
 
     drawChart(week, sgvData, options);