Chart.js Dynamically Updating Chart with X Axis Time
PhilBot
I'm using Chart.js version 2.7.1 and I am dynamically updating my Line chart when temperature data comes in.
The problem is that the lines never pass the halfway mark of the x axis in time. Every time I update, the chart auto scales the right side ( max time ) of the x axis to be further out, so my data never approaches the right side of the chart. What I want is for the line to approach the right side, and only a small margin of time is extended into the future for the x-axis each time I update. How can I accomplish this? Thanks.
Here is how I configure the chart:
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: [],
label: 'Hot Temperature',
backgroundColor: "#FF2D00",
borderColor: "#FF2D00",
type: 'line',
pointRadius: 1,
lineTension: 2,
borderWidth: 2
},
{
fill: false,
data: [],
label: 'Cold Temperature',
backgroundColor: "#0027FF",
borderColor: "#0027FF",
type: 'line',
pointRadius: 1,
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 )'
},
}]
}
}
});
Here is the chart: 
Fabrizio Bertoglio
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',
pointRadius: 1,
lineTension: 2,
borderWidth: 2
},
{
fill: false,
data: getColdTempData(),
label: 'Cold Temperature',
backgroundColor: "#0027FF",
borderColor: "#0027FF",
type: 'line',
pointRadius: 1,
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>Collected from the Internet
Please contact [email protected] to delete if infringement.
edited at
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