score:2

as you can see in the following snippet and thanks also to Daniel W Strimpel for creating the initial snippet, you problem is in the hot and cold temperature `data`.

``````{ x: new Date(2019, 0, 1, 14, 1, 19, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 20, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 21, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 22, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 23, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 24, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 25, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 26, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 27, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 28, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 29, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 30, 0) }
``````

both of those arrays have `n` number of entries in the end missing the `y` coordinate including the temperature value. I recreated your scenario by deleting the `y` for the 5 last entries of the cold and hot temperatures `data`.

The `chart` will add the date to the `x axis`, but it will not add a `temperature` value and the line will not show up.

``````{x: new Data(2019, 0, 14, 1, 26, 0) }
``````

The code snippet recreates your scenario, you can run it to understand the problem and fix it by adding the `y` value to the last 5 entries in the `getHotTempData` and `getColdTempData`

``````var ctx = document.getElementById('tempChart').getContext('2d');
ctx.canvas.width = 320;
ctx.canvas.height = 240;

var chart = new Chart(ctx, {
type: 'line',
data: {
labels: [],
legend: {
display: true
},
datasets: [{
fill: false,
data: getHotTempData(),
label: 'Hot Temperature',
backgroundColor: "#FF2D00",
borderColor: "#FF2D00",
type: 'line',
lineTension: 2,
borderWidth: 2
},
{
fill: false,
data: getColdTempData(),
label: 'Cold Temperature',
backgroundColor: "#0027FF",
borderColor: "#0027FF",
type: 'line',
lineTension: 2,
borderWidth: 2
}]
},
options: {
animation: false,
responsive: true,
scales: {
xAxes: [{
scaleLabel: {
display: true,
labelString: 'Time ( UTC )'
},
type: 'time',
time: {
tooltipFormat: "hh:mm:ss",
displayFormats: {
hour: 'MMM D, hh:mm:ss'
}
},
ticks: {
maxRotation: 90,
minRotation: 90
}
}],
yAxes: [{
scaleLabel: {
display: true,
labelString: 'Temperature ( Celcius )'
},
}]
}
}
});

function getHotTempData() {
return [
{ x: new Date(2019, 0, 1, 14, 1, 19, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 20, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 21, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 22, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 23, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 24, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 25, 0), y: Math.random() * 0.5 + 35 },
{ x: new Date(2019, 0, 1, 14, 1, 26, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 27, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 28, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 29, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 30, 0) }
];
}

function getColdTempData() {
return [
{ x: new Date(2019, 0, 1, 14, 1, 19, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 20, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 21, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 22, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 23, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 24, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 25, 0), y: Math.random() * 0.5 + 23.5 },
{ x: new Date(2019, 0, 1, 14, 1, 26, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 27, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 28, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 29, 0) },
{ x: new Date(2019, 0, 1, 14, 1, 30, 0) }
];
}``````
``````<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment-with-locales.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.3/Chart.min.js"></script>
<canvas id="tempChart"></canvas>``````