Odd animation with multiple series - animation

Question

I was trying to adapt the spline animation for time series (https://www.highcharts.com/demo/dynamic-update) for multiple series.
I modified the example here https://jsfiddle.net/2wj3fquL/
Highcharts.chart('container', {
chart: {
type: 'spline',
animation: Highcharts.svg, // don't animate in old IE
marginRight: 10,
events: {
load: function () {
// set up the updating of the chart each second
var series = this.series;
setInterval(function () {
var x = (new Date()).getTime(), // current time
y = Math.random();
series[0].addPoint([x, y], true, true);
y = Math.random();
series[1].addPoint([x, y], true, true);
}, 1000);
}
}
},
time: {
useUTC: false
},
title: {
text: 'Live random data'
},
accessibility: {
announceNewData: {
enabled: true,
minAnnounceInterval: 15000,
announcementFormatter: function (allSeries, newSeries, newPoint) {
if (newPoint) {
return 'New point added. Value: ' + newPoint.y;
}
return false;
}
}
},
xAxis: {
type: 'datetime',
tickPixelInterval: 150
},
yAxis: {
title: {
text: 'Value'
},
plotLines: [{
value: 0,
width: 1,
color: '#808080'
}]
},
tooltip: {
headerFormat: '<b>{series.name}</b><br/>',
pointFormat: '{point.x:%Y-%m-%d %H:%M:%S}<br/>{point.y:.2f}'
},
legend: {
enabled: false
},
exporting: {
enabled: false
},
series: [{
name: 'Random data',
data: (function () {
// generate an array of random data
var data = [],
time = (new Date()).getTime(),
i;
for (i = -19; i <= 0; i += 1) {
data.push({
x: time + i * 1000,
y: Math.random()
});
}
return data;
}())
}, {
name: 'other data',
data: (function () {
// generate an array of random data
var data = [],
time = (new Date()).getTime(),
i;
for (i = -19; i <= 0; i += 1) {
data.push({
x: time + i * 1000,
y: Math.random()
});
}
return data;
}())
}]
});
Unfortunately the effect is odd since one series moves smooth while the other doesn't ...
How could I solve this problem?
Thanks

Answer 1

That is because the chart is redrawn twice. Disable redraw in the first addPoint method call.
events: {
load: function() {
...
setInterval(function() {
...
series[0].addPoint([x, y], false, true);
series[1].addPoint([x, y], true, true);
}, 1000);
}
}
Live demo: https://jsfiddle.net/BlackLabel/0n2yw57m/
API Reference: https://api.highcharts.com/class-reference/Highcharts.Series#addPoint