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I am having some issues when I am trying to display a min/max range of hours in the x-axis of a bar graph with Chart.js. Now it is showing the whole time range of 24 hours. I want the range to be between 06:00-23:00, but I can only access this if I declare a specific daterange aswell like this:
xAxes: {
ticks: {
},
type: 'time',
time: {
unit: 'hour',
displayFormats: {
hour: 'HH:mm',
},
},
min: '2022-10-21T06:00:00',
max: '2022-10-21T23:00:00',
},
But I want to display the time range, without having to declare a date range, and I thought it would be logic to declare it like this, but it is not:
min: 'YYYY-MM-DDT06:00:00',
max: 'YYYY-MM-DDT23:00:00',
Does anyone have any ideas how to solve this?
How I want it to be displayed
max and min are defined directly on the axis but not inside the time option.
For further information, consult Min Max Configuration from the Chart.js documentation.
Please take a look at below runnable code snippet and see how it works.
new Chart('chart', {
type: 'bar',
data: {
datasets: [{
label: '# of Votes',
data: [
{x: '2022-10-03T07', y: 10},
{x: '2022-10-03T08', y: 15},
{x: '2022-10-03T10', y: 8},
{x: '2022-10-03T12', y: 12},
{x: '2022-10-03T13', y: 13},
{x: '2022-10-03T18', y: 7}
],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
}]
},
options: {
scales: {
x: {
type: 'time',
time: {
unit: 'hour',
displayFormats: {
hour: 'HH:mm',
},
tooltipFormat: 'd MMM yyyy HH:mm'
},
min: '2022-10-03T06',
max: '2022-10-03T23'
}
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.9.1/chart.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.2/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/chartjs-adapter-moment/1.0.0/chartjs-adapter-moment.min.js"></script>
<canvas id="chart" height="85"></canvas>
I'm new to Vue3 and Chart.js and I couldn't figure out how to solve this issue. I'm keep getting the same error over and over. Can someone please help me?
TypeError: Cannot read properties of null (reading 'getContext')
Here is my template:
<template>
<div class="border border-dark rounded container m-2">
<canvas id="myChart" width="400" height="400"></canvas>
</div>
</template>
and my script:
import Chart from 'chart.js/auto'
export default {
mounted() {
const ctx = document.getElementById("myChart").getContext('2d');
const myChart = new Chart(ctx, {
type: 'bar',
data: {
labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
datasets: [{
label: '# of Votes',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
}]
},
options: {
scales: {
y: {
beginAtZero: true
}
}
}
});
console.log('mounted')
}
And I have one more question, when I run this code I get null. Is this normal?
console.log(document.getElementById("myChart"))
This seems pretty straightforward but I'm not understanding why it's not rendering the chart correctly. Is there a way to pass the configuration section below to a new chart as a variable? If I load the chart using the coding below it works perfectly. I've tried putting the configuration section into a variable and then placing that within the configuration section, surrounding it by brackets. When I do there's no errors it's just blank like it's not receiving it correctly.
new Chart(myCanvas, {type: 'bar',
data: {
labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
datasets: [{
label: '# of Votes',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
}]
},
options: {
scales: {
y: {
beginAtZero: true
}
}
}})
you must add document.getElementById("MyChart") inside Chart() object and you will get something like this
<script src="https://cdn.jsdelivr.net/npm/chart.js#3.6.0/dist/chart.min.js"></script>
<canvas id="MyChart" width="400" height="200"></canvas>
<script>
new Chart(document.getElementById("MyChart"), {type: 'bar',
data: {
labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
datasets: [{
label: '# of Votes',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
}]
},
options: {
scales: {
y: {
beginAtZero: true
}
}
}})
;
</script>
I have a chart.js line chart where the x axis labels are plain old numbers, e.g. [2,4,15,45,90], which represent days on this chart. I don't want the x-axis ticks to mirror the data labels, i want the ticks to be at interval of 20. How can I achieve this?
This in my options does nothing:
xAxes: [ {
display: true,
position: 'bottom',
ticks: {
stepSize: 20,
min: 0,
max: 140
}
],
example here: jsfiddle
...the only (awful) way i found is to turn the numbers into dates and in the ticks callback, calculate the number of days difference. as seen here
You could use a scatter chart that accepts the data as individual points, objects with properties x and y. To turn a scatter chart back to a line chart, simply define showLine: true on each dataset.
To product data as individual points, you can defined labels outside of the chart and convert both value arrays using Array.map() as follows.
valueArray.map((v, i) => ({ x: labels[i], y: v }))
The last thing to do is defining xAxis.ticks as follows:
ticks: {
stepSize: 1,
autoSkip: false,
callback: value => value % 20 == 0 ? value : null,
min: labels[0],
max: labels[labels.length - 1],
maxRotation: 0
},
Please have a look at your amended code below:
const labels = [7, 14, 21, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105, 119, 126];
var myChart = new Chart('myChart', {
type: 'scatter',
data: {
datasets: [{
label: 'IC',
data: [9432.13209267, 1899.132847, 851.2122668, 3964.48968367, 9433, 8087.04121533, 1268.34642367, 825.29800317, 4271.00722867, 1157.57453933, 4928.214994, 783.88204033, 1846.623016, 4001.84214867, 709.70201067, 3917.61792167, 688.1571182].map((v, i) => ({ x: labels[i], y: v })),
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255,99,132,1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
showLine: true,
borderWidth: 1
},
{
label: 'Mtb',
data: [14241.41334667, 48348.08833, 5055.28134533, 7614.80689233, 14240, 24536.66203, 1083.99264, 144.72451603, 15968.94539333, 160.150183, 5127.77524033, 953.9963646, 0, 2989.36556, 21.32920023, 27.03159138, 60310.22952333].map((v, i) => ({ x: labels[i], y: v })),
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255,99,132,1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
showLine: true,
borderWidth: 1
}
]
},
options: {
scales: {
xAxes: [{
display: true,
position: 'bottom',
ticks: {
stepSize: 1,
autoSkip: false,
callback: value => value % 20 == 0 ? value : null,
min: labels[0],
max: labels[labels.length - 1],
maxRotation: 0
},
// afterBuildTicks: (axis, ticks) => [0, 20, 40, 60, 80, 100, 120],
scaleLabel: {
display: true,
labelString: 'Days from initial test',
fontSize: 16
}
}],
yAxes: [{
display: true,
position: 'left',
ticks: {
beginAtZero: true,
stepSize: 10000,
min: 0,
max: 70000
},
scaleLabel: {
display: true,
fontSize: 16
}
},
{
display: true,
position: 'right',
ticks: {
beginAtZero: true,
stepSize: 10000,
min: 0,
max: 70000
},
scaleLabel: {
display: true,
fontSize: 16
}
},
]
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js"></script>
<canvas id="myChart" height="100"></canvas>
See attached screenshot with an example with what I'm trying to do.
Basically I want to be able to add custom text on certain yAxis and xAxis lines.
You can use the Plugin Core API. It offers different hooks that may be used for executing custom code. In below code snippet, I use the afterDraw hook to draw custom text on the canvas.
For positioning your text on x and y, you may use hard coded number of pixels or compute them using the Scale Interface (i.e. function getPixelForValue).
new Chart(document.getElementById('myChart'), {
type: 'bar',
plugins: {
afterDraw: chart => {
var ctx = chart.chart.ctx;
var xAxis = chart.scales['x-axis-0'];
var yAxis = chart.scales['y-axis-0'];
ctx.save();
ctx.font = "18px Arial";
ctx.fillStyle = "red";
var x = (xAxis.getPixelForValue('May') + xAxis.getPixelForValue('June')) / 2;
ctx.fillText('My custom text here', x, yAxis.getPixelForValue(65));
ctx.fillText('Another custom text here', 30, 15);
ctx.restore();
}
},
data: {
labels: ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
datasets: [{
label: "My First Dataset",
data: [65, 59, 80, 81, 56, 55, 40],
fill: false,
backgroundColor: ['rgba(255, 99, 132, 0.2)', 'rgba(255, 159, 64, 0.2)', 'rgba(255, 205, 86, 0.2)', 'rgba(75, 192, 192, 0.2)', 'rgba(54, 162, 235, 0.2)', 'rgba(153, 102, 255, 0.2)', 'rgba(201, 203, 207, 0.2)'],
borderColor: ['rgb(255, 99, 132)', 'rgb(255, 159, 64)', 'rgb(255, 205, 86)', 'rgb(75, 192, 192)', 'rgb(54, 162, 235)', 'rgb(153, 102, 255)', 'rgb(201, 203, 207)'],
borderWidth: 1
}]
},
options: {
scales: {
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js"></script>
<canvas id="myChart" height="110"></canvas>