Develop Reference

Chart.js Treemap Custom text

In my code below, I am able to draw a Treemap and also display the tag in each tree cell. But I want to add some custom text next to my tag,
Like say I want the word 'Language' to appear in each tree map cell. I tried the formatter options, But its not working for the version of chart.js I am using. Kindly provide me a solution for the specific version I am using. Since I have multiple other charts defined and changing the version would cause issues.
var topTags = [
{tag:'android',num:42657},{tag:'reactjs',num:38844},{tag:'php',num:34381},{tag:'sql',num:29996},
];
var canvas = document.getElementById("treemap");
var ctx = canvas.getContext("2d");
var chart = window.chart = new Chart(ctx, {
type: "treemap",
data: {
datasets: [{
tree: topTags,
key: "num",
groups: ['tag'],
spacing: 0.5,
borderWidth: 1.5,
fontColor: "black",
borderColor: "grey"
}]
},
options: {
maintainAspectRatio: false,
legend: { display: false },
tooltips: { enabled: false }
}
});
CHART.JS AND TREEMAP VERSION :
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/chartjs-chart-treemap#0.2.3"></script>

The formatter option only got added in version 2 of the treemap chart type, the scriptable option is only available in version 1 so the best way for you to get the extra text is by editing your original data array first and adding the text to it that way like so:
let topTags = [{
tag: 'android',
num: 42657
}, {
tag: 'reactjs',
num: 38844
}, {
tag: 'php',
num: 34381
}, {
tag: 'sql',
num: 29996
}, ];
topTags = topTags.map(e => ({
num: e.num,
tag: `Lang: ${e.tag}`
}))
const canvas = document.getElementById("chart");
const ctx = canvas.getContext("2d");
const chart = window.chart = new Chart(ctx, {
type: "treemap",
data: {
datasets: [{
tree: topTags,
key: "num",
groups: ['tag'],
spacing: 0.5,
borderWidth: 1.5,
fontColor: "black",
borderColor: "grey",
}]
},
options: {
maintainAspectRatio: false,
legend: {
display: false
},
tooltips: {
enabled: false
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/chartjs-chart-treemap#0.2.3"></script>
<canvas id="chart"></canvas>

Styling problems with Chart.Js

How can I add these styles to my graph? I'm having trouble finding it in the documentation for it, and the other forums aren't very helpful. I am using Flask for the backend, so that's why the data values look like that.
Labels on top of bars
Change font size on both axis
Set y scale as a fixed value (0,8)
<script>
var ctx = document.getElementById('myChart').getContext('2d');
var options = {
scales: {
yAxes: [{
ticks: {
fontSize: 40
}
}]
}
}
var myChart = new Chart(ctx, {
type: 'bar',
data: {
labels: ['Lithium Battery', 'Other Mfg', 'Delivery', 'Tailpipe', 'Fuel Cycle', 'Disposal', 'Total'],
datasets: [{
label: 'ICEV CAR (MTCO2e/Year)',
labels: [
"{{data['battery_icev_car']}}",
"{{data['other_mfg_icev_car']}}",
"{{data['delivery_icev_car']}}",
"{{data['tailpipe_icev_car']}}",
"{{data['fuel_cycle_icev_car']}}",
"{{data['disposal_icev_car']}}",
"{{data['total_icev_car']}}"
],
data: [ /* errors are normal, fixes when server ru
[0, {{data['y1_icev']}}],
[{{data['y1_icev']}}, {{data['y2_icev']}}],
[{{data['y2_icev']}}, {{data['y3_icev']}}],
[{{data['y3_icev']}}, {{data['y4_icev']}}],
[{{data['y4_icev']}}, {{data['y5_icev']}}],
[{{data['y5_icev']}}, {{data['y6_icev']}}],
[0, {{data['y6_icev']}}]
],
backgroundColor: [
'rgba(0,0,0,0.9)'
],
borderColor: [
'rgba(0,0,0,1)'
],
borderWidth: 1,
borderSkipped: false
}]
},
options: {
responsive: true,
plugins: {
legend: {
labels: {
// This doesn't work on axis
font: {
size: 20
}
}
}
},
y: {
beginAtZero: true
}
}
});
</script> </script>

Since your config is not working I assume you are using V3, in which case the solution is as followed:
For point one you need to use an external plugin, you can write your own or use the datalabels plugin
For your second problem you need to style it as a font object as told in the documentation like so:
options: {
scales: {
y:{
ticks:{
font:{
size: 50
}
}
}
}
}
For your last part you can set the stepSize to 0.8

Chart.js - change which data the legend uses for the coloured box

I have a bar chart that always shows 4 bars. The bars are coloured dynamically. It looks like the coloured box takes its colour from the first data. I would like to use the colour from the 4th (last) data value. Maybe the options:plugins:legend:label:sort function helps but I don't understand what it does.
options
const options = {
scales: {
x: {
grid: {
display: false,
color: 'rgba(0,0,0)'
}
},
y: {
display: false,
min: 0,
max: 4
},
},
plugins: {
legend: {
position: 'bottom'
}
}
}
So I don't know if I can change the data that the box color comes from, or if there is a config option somewhere where I can change it manually.

You can use the generateLabels function as described here.
Please take a look at below runnable sample code and see how it works.
new Chart('myChart', {
type: 'bar',
data: {
labels: ['Red', 'Blue', 'Yellow'],
datasets: [{
label: 'My Dataset',
data: [300, 50, 100],
backgroundColor: ['#FF6384', '#36A2EB', '#FFCE56']
}]
},
options: {
responsive: false,
plugins: {
legend: {
labels: {
generateLabels: chart => {
let ds = chart.data.datasets[0];
let color = ds.backgroundColor[ds.backgroundColor.length - 1];
return [{
datasetIndex: 0,
text: ds.label,
fillStyle: color,
strokeStyle: color
}];
}
}
}
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.5.1/chart.min.js"></script>
<canvas id="myChart" height="180"></canvas>

Following up with #uminder's answer, if you want to keep the hide/show chart and the line-through style after clicking on the legend, you can add the following line:
options: {
responsive: false,
plugins: {
legend: {
labels: {
generateLabels: chart => {
let ds = chart.data.datasets[0];
let color = ds.backgroundColor[ds.backgroundColor.length - 1];
return [{
datasetIndex: 0,
text: ds.label,
fillStyle: color,
strokeStyle: color,
+ hidden: !chart.isDatasetVisible(0)
}];
}
}
}
}
}

chart.js plotting timeseries

Attempting to pass through data from django to a webpage to render a responsive chart. The data are being passed correctly to js, but I am driving myself crazy trying to understand why charts.js is throwing an error.
I have hardcoded some data for example:
function setLineChart() {
var ctx = document.getElementById("myLineChart").getContext('2d');
var dat_1 = {
label: 'things',
borderColor: 'blue',
data: [
{t: new Date("04/01/2020"), y: 310},
{t: new Date("04/02/2020"), y: 315},
{t: new Date("04/03/2020"), y: 320},
]
};
var myLineChart = new Chart(ctx, {
type: 'line',
data: {
datasets: [dat_1]
},
options: {
scales: {
xAxes: [{
type: 'time',
time: {
unit: 'day'
},
}],
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
}
})
}
<canvas id="myLineChart" width="600" height="600"></canvas>
And this returns a Uncaught TypeError: Cannot read property 'skip' of undefined error that I can't debug. setLineChart() gets called as part of an ajax response on a form update. When I comment out the options section, it does render a chart, but misses off the last data point, and has undefined as the x-axis marker.
Any help would be appreciated.

Chart.js internally uses Moment.js for the functionality of the time axis. Therefore you should use the bundled version of Chart.js that includes Moment.js in a single file.
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.bundle.min.js"></script>
This will solve your problem as the following amended code snippet illustrates.
var ctx = document.getElementById("myLineChart").getContext('2d');
var dat_1 = {
label: 'things',
borderColor: 'blue',
data: [
{ t: new Date("04/01/2020"), y: 310 },
{ t: new Date("04/02/2020"), y: 315 },
{ t: new Date("04/03/2020"), y: 320 },
]
};
var myLineChart = new Chart(ctx, {
type: 'line',
data: {
datasets: [dat_1]
},
options: {
scales: {
xAxes: [{
type: 'time',
time: {
unit: 'day'
},
}],
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.bundle.min.js"></script>
<canvas id="myLineChart" height="90"></canvas>

How to show bar labels in legend in Chart.js 2.1.6?

I'm creating charts using Chart.js and I want to show the labels for the bars in the legend, not the title of the dataset (there is only one), please see the below image as an example:
My current legend just looks like this:
I have looked through the docs but to no avail, I found them very confusing actually.
Here is my current code:
var chart_0 = new Chart($('#cp_chart_0'), {
type: 'bar'
, data: {
labels: ['Blue','Green','Yellow','Red','Purple','Orange']
, datasets: [{
label: 'Dataset 1'
, borderWidth: 0
, backgroundColor: ['#2C79C5','#7FA830','#7B57C3','#ED4D40','#EC802F','#1DC6D3']
, data: ['12','2','5','0','9','1']
}]
}
});
Thanks!

In one of the most recent releases of Chart.js 2.1.x, they added back this functionality. So go get the latest release first. Then insert the code below.
It is located under the options and legend. Here is how you use it:
options: {
legend: {
position: 'right'
}
}

Easiest way is to provide your data with multiple sets :
data: {
labels: ['total votes']
, datasets: [{
label: 'Blue'
, backgroundColor: ['#2C79C5']
, data: ['12']
},{
label: 'Green'
, backgroundColor: ['#7FA830']
, data: ['2']
},
...
]
}
But you can generate a custom labels using generateLabels - http://www.chartjs.org/docs/#chart-configuration-legend-configuration
Or even customise the whole legend, including formatting, with legendCallback - http://www.chartjs.org/docs/#chart-configuration-common-chart-configuration

This solution uses Chart.js version 3. You can pre-process your data using the Plugin Core API. The API offers different hooks that may be used for executing custom code.
I use the beforeInit hook to create individual datasets for each defined label/value pair. Note that the data of these new datasets are defined in point format (for instance [{ x: 1, y: 12 }]):
beforeInit: chart => {
let dataset = chart.config.data.datasets[0];
chart.config.data.datasets = chart.config.data.labels.map((l, i) => ({
label: l,
data: [{ x: i + 1, y: dataset.data[i] }],
backgroundColor: dataset.backgroundColor[i],
categoryPercentage: 1
}));
chart.config.data.labels = undefined;
}
Further you need to define a second x-axis that will contain the labels.
x1: {
offset: true,
gridLines: {
display: false
}
}
The labels on x1 need to be collected and defined programmatically each time the hidden state of a dataset changes. This can be done in the beforeLayout hook.
beforeLayout: chart => chart.options.scales.x1.labels = chart.config.data.datasets.filter((ds, i) => !chart.getDatasetMeta(i).hidden).map(ds => ds.label)
Please take a look at below runnable code and see how it works.
new Chart('chart', {
type: 'bar',
plugins: [{
beforeInit: chart => {
let dataset = chart.config.data.datasets[0];
chart.config.data.datasets = chart.config.data.labels.map((l, i) => ({
label: l,
data: [{ x: i + 1, y: dataset.data[i] }],
backgroundColor: dataset.backgroundColor[i],
categoryPercentage: 1
}));
chart.config.data.labels = undefined;
},
beforeLayout: chart => chart.options.scales.x1.labels = chart.config.data.datasets.filter((ds, i) => !chart.getDatasetMeta(i).hidden).map(ds => ds.label)
}],
data: {
labels: ['Blue', 'Green', 'Yellow', 'Red', 'Purple', 'Orange'],
datasets: [{
data: ['12', '2', '5', '0', '9', '1'],
backgroundColor: ['#2C79C5', '#7FA830', '#FFF200', '#ED4D40', '#800080', '#EC802F']
}]
},
options: {
interaction: {
intersect: true,
mode: 'nearest'
},
plugins: {
legend: {
position: 'right'
},
tooltip: {
callbacks: {
title: () => undefined
}
}
},
scales: {
y: {
beginAtZero: true
},
x: {
display: false
},
x1: {
offset: true,
gridLines: {
display: false
}
}
}
}
});
canvas {
max-width: 400px;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.2.0/chart.min.js"></script>
<canvas id="chart" height="120"></canvas>