Develop Reference

How to create custom legend in ChartJS

I need to create custom legend for my donut chart using ChartJS library.
I have created donut with default legend provided by ChartJS but I need some modification.
I would like to have value above the car name. Also I don't like sticky legend I want to have it separate from donut so I can change the style for fonts, boxes (next to the text "Audi" for example)
I know there is some Legend generator but I'm not sure how to use it with VueJS - because I'm using VueJS as a framework
This is how my legend looks like now - http://imgur.com/a/NPUoi
My code:
From Vue component where I import a donut component:
<div class="col-md-6">
<div class="chart-box">
<p class="chart-title">Cars</p>
<donut-message id="chart-parent"></donut-message>
</div>
</div>
Javascript:
import { Doughnut } from 'vue-chartjs'
export default Doughnut.extend({
ready () {
Chart.defaults.global.tooltips.enabled = false;
Chart.defaults.global.legend.display = false;
this.render({
labels: ['Audi','BMW','Ford','Opel'],
datasets: [
{
label: 'Cars',
backgroundColor: ['#35d89b','#4676ea','#fba545','#e6ebfd'],
data: [40, 30, 20, 10]
}
]
},
{
responsive: true,
cutoutPercentage: 75,
legend: {
display: true,
position: "right",
fullWidth: true,
labels: {
boxWidth: 10,
fontSize: 14
}
},
animation: {
animateScale: true
}
})
}
});

I'm having the same problem trying to understand the documentation and this link might clarify the process of customize the legends:
https://codepen.io/michiel-nuovo/pen/RRaRRv
The trick is to track a callback to build your own HTML structure and return this new structure to ChartJS.
Inside the options object:
legendCallback: function(chart) {
var text = [];
text.push('<ul class="' + chart.id + '-legend">');
for (var i = 0; i < chart.data.datasets[0].data.length; i++) {
text.push('<li><span style="background-color:' +
chart.data.datasets[0].backgroundColor[i] + '">');
if (chart.data.labels[i]) {
text.push(chart.data.labels[i]);
}
text.push('</span></li>');
}
text.push('</ul>');
return text.join("");
}
Second, you need a container to insert the new html and using the method myChart.generateLegend() to get the customized html:
$("#your-legend-container").html(myChart.generateLegend());
After that, if you need, track down the events:
$("#your-legend-container").on('click', "li", function() {
myChart.data.datasets[0].data[$(this).index()] += 50;
myChart.update();
console.log('legend: ' + data.datasets[0].data[$(this).index()]);
});
$('#myChart').on('click', function(evt) {
var activePoints = myChart.getElementsAtEvent(evt);
var firstPoint = activePoints[0];
if (firstPoint !== undefined) {
console.log('canvas: ' +
data.datasets[firstPoint._datasetIndex].data[firstPoint._index]);
}
else {
myChart.data.labels.push("New");
myChart.data.datasets[0].data.push(100);
myChart.data.datasets[0].backgroundColor.push("red");
myChart.options.animation.animateRotate = false;
myChart.options.animation.animateScale = false;
myChart.update();
$("#your-legend-container").html(myChart.generateLegend());
}
}
Another solution that I found, if you don't need to change the HTMl structure inside the legend, you can just insert the same HTML in your legend container and customize it by CSS, check this another link:
http://jsfiddle.net/vrwjfg9z/
Hope it works for you.

You can extract the legend markup.
data () {
return {
legendMarkup: ''
}
},
ready () {
this.legendMarkup = this._chart.generateLegend()
}
And in your template you can output it.
<div class="legend" ref="legend" v-html="legendMarkup"></div>
this._chart is the internal chartjs instance in vue-chartjs. So you can call all chartjs methods which are not exposed by vue-chartjs api over it.
However you can also use the legend generator. The usage is the same in vue. You can pass in the options, use callbacks etc.

please check this documentation
.
Legend Configuration
The chart legend displays data about the datasets that area appearing on the chart.
Configuration options
Position of the legend. Options are:
'top'
'left'
'bottom'
'right'
Legend Item Interface
Items passed to the legend onClick function are the ones returned from labels.generateLabels. These items must implement the following interface.
{
// Label that will be displayed
text: String,
// Fill style of the legend box
fillStyle: Color,
// If true, this item represents a hidden dataset. Label will be rendered with a strike-through effect
hidden: Boolean,
// For box border. See https://developer.mozilla.org/en/docs/Web/API/CanvasRenderingContext2D/lineCap
lineCap: String,
// For box border. See https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/setLineDash
lineDash: Array[Number],
// For box border. See https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineDashOffset
lineDashOffset: Number,
// For box border. See https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineJoin
lineJoin: String,
// Width of box border
lineWidth: Number,
// Stroke style of the legend box
strokeStyle: Color
// Point style of the legend box (only used if usePointStyle is true)
pointStyle: String
}
Example
The following example will create a chart with the legend enabled and turn all of the text red in color.
var chart = new Chart(ctx, {
type: 'bar',
data: data,
options: {
legend: {
display: true,
labels: {
fontColor: 'rgb(255, 99, 132)'
}
}
}
});
Custom On Click Actions
It can be common to want to trigger different behaviour when clicking an item in the legend. This can be easily achieved using a callback in the config object.
The default legend click handler is:
function(e, legendItem) {
var index = legendItem.datasetIndex;
var ci = this.chart;
var meta = ci.getDatasetMeta(index);
// See controller.isDatasetVisible comment
meta.hidden = meta.hidden === null? !ci.data.datasets[index].hidden : null;
// We hid a dataset ... rerender the chart
ci.update();
}
Lets say we wanted instead to link the display of the first two datasets. We could change the click handler accordingly.
var defaultLegendClickHandler = Chart.defaults.global.legend.onClick;
var newLegendClickHandler = function (e, legendItem) {
var index = legendItem.datasetIndex;
if (index > 1) {
// Do the original logic
defaultLegendClickHandler(e, legendItem);
} else {
let ci = this.chart;
[ci.getDatasetMeta(0),
ci.getDatasetMeta(1)].forEach(function(meta) {
meta.hidden = meta.hidden === null? !ci.data.datasets[index].hidden : null;
});
ci.update();
}
};
var chart = new Chart(ctx, {
type: 'line',
data: data,
options: {
legend: {
}
}
});
Now when you click the legend in this chart, the visibility of the first two datasets will be linked together.
HTML Legends
Sometimes you need a very complex legend. In these cases, it makes sense to generate an HTML legend. Charts provide a generateLegend() method on their prototype that returns an HTML string for the legend.
To configure how this legend is generated, you can change the legendCallback config property.
var chart = new Chart(ctx, {
type: 'line',
data: data,
options: {
legendCallback: function(chart) {
// Return the HTML string here.
}
}
});

c3.js - c3 graph that has a tooltip with a c3 graph inside

I have a c3.js line graph that represents the evolution of 2 values. I need that the tooltip of the line graph to be a pie chart (tooltip = another c3.js graph).
Here is what I succeeded:
http://jsfiddle.net/owhxgaqm/80/
// c3 - custom tooltip
function generateGraph(data1,data2) {
console.log(data1.name + '\t' + data1.value + '\t' + data2.name + '\t' + data2.value);
var chart1 = c3.generate(
{
bindto: "#t",
data: {columns : [[data1.name, data1.value],[data2.name, data2.value]],
type : 'pie'}
});
}
var chart = c3.generate({
data: {
columns: [
['data1', 1000, 200, 150, 300, 200],
['data2', 400, 500, 250, 700, 300], ]
},
tooltip: {
contents: function (d, defaultTitleFormat, defaultValueFormat, color) {
generateGraph(d[0], d[1]);
var divt = document.getElementById("t");
return '';
}
}
});
As you can see I'm binding the "tooltip" with an already existing div so this is not really what I want from c3.js.
Any idea is welcome.
Thanks.

Adding a Chart inside a C3 Tooltip
You can use the tooltip element that c3 already has. In your contents function call the generateGraph function (see next step). Pass in the tooltip element available in this.tooltip in addition to the data.
...
tooltip: {
contents: function (d) {
// this creates a chart inside the tooltips
var content = generateGraph(this.tooltip, d[0], d[1])
// we don't return anything - see .html function below
}
}
...
Your generateGraph function basically creates a c3 chart in your tooltip element (bindto supports a d3 element). We do a bit of optimization (if the data is same, the chart is not recreated) and cleanup (when a chart is recreated it is destroyed and removed from the DOM)
function generateGraph(tooltip, data1, data2) {
// if the data is same as before don't regenrate the graph - this avoids flicker
if (tooltip.data1 &&
(tooltip.data1.name === data1.name) && (tooltip.data1.value === data1.value) &&
(tooltip.data2.name === data2.name) && (tooltip.data2.value === data2.value))
return;
tooltip.data1 = data1;
tooltip.data2 = data2;
// remove the existing chart
if (tooltip.chart) {
tooltip.chart = tooltip.chart.destroy();
tooltip.selectAll('*').remove();
}
// create new chart
tooltip.chart = c3.generate({
bindto: tooltip,
size: {
width: 200,
height: 200
},
data: {
columns: [[data1.name, data1.value], [data2.name, data2.value]],
type: 'pie'
}
});
// creating a chart on an element sets its position attribute to relative
// reset it to absolute (the tooltip was absolute originally) for proper positioning
tooltip.style('position', 'absolute');
}
Note that we set the chart size so that it's more like tooltip content instead of a subchart.
The last bit is a bit hacky - since c3 requires that we set a HTML (which we don't want to do) and because we don't have any other callbacks we can easily hitch onto after the content handler, we have to disable the function that c3 uses to set the html content on the tooltip (this will affect only this chart's tooltip) i.e. .tooltip.html
// MONKEY PATCHING (MAY break if library updates change the code that sets tooltip content)
// we override the html function for the tooltip to not do anything (since we've already created the tooltip content inside it)
chart.internal.tooltip.html = function () {
// this needs to return the tooltip - it's used for positioning the tooltip
return chart.internal.tooltip;
}
Fiddle - http://jsfiddle.net/muuqvf1a/
Tooltip Positioning
Instead of using c3's tooltip positioning you could also size and position the tooltip at the bottom of the chart. Just style .c3-tooltip-container.
Alternatives
Note that c3 also support subcharts (http://c3js.org/reference.html#subchart-show) and data.mouseover (http://c3js.org/reference.html#data-onmouseover) which could also be a cleaner avenues worth exploring.

highstocks - legend position and refresh legend values on mousemove of multiple charts

Here is the scenario. I've multiple highstocks say 10 charts on a single page. Currently I've written 500 lines of code to position the legend, show tooltip and refresh the legend values on mousemove.
No. of legends vary per chart. On mousemove values of all the legends are updated. I need to optimize the code I am using highstocks v1.2.2.
Above screenshot shows 2 charts. Return, Basket, vs Basket Spread are legends and it's values are updated on every mousemove.
Please find this fiddle for example. In my case legends are positioned and updated values on mouse move with hundreds of lines of code. When I move the mouse the legend values of Return and Basket of first chart and the legend values of vs Basket Spread are updated. It's working fine but with lots of javascript code. So I need to optimize it less code or with highstocks built-in feature.
Update
User #wergeld has posted new fiddle. As I've shown in screenshot when cross-hair is being moved over any chart, the legend values of all the charts should be updated.
Is there anyway to implement the same functionality with less code or is there built-in feature available in highstocks ???
Using this as a reference.

Basic example would be to use the events.mouseover methods:
plotOptions: {
series: {
point: {
events: {
mouseOver: function () {
var theLegendList = $('#legend');
var theSeriesName = this.series.name;
var theYValue = this.y;
$('li', theLegendList).each(function (l) {
if (this.innerText.split(':')[0] == theSeriesName) {
this.innerText = theSeriesName + ': ' + theYValue;
}
});
}
}
}
}
}
This is assuming I have modded the <li> to be:
$('<li>')
.css('color', serie.color)
.text(serie.name + ': NA')
.click(function () {
toggleSeries(i);
})
.appendTo($legend);
You would then need to handle the mouseout event but I do not know what you want to do there.
Working example.
EDIT:
Here is a version using your reference OHLC chart to put the values in a different legend location when any point in the chart is hovered.
plotOptions: {
series: {
point: {
events: {
mouseOver: function () {
//using the ohlc and volumn data sets created at runtime.
var stockVal = ohlc[this.index][4]; // show close value
var stockVolume = volume[this.index][1];
var theChart = $('#container').highcharts();
var theLegendList = $('#legend');
$('li', theLegendList).each(function (l) {
var legendTitle = theChart.series[l].name;
if (l === 0) {
this.innerText = legendTitle + ': ' + stockVal;
}
if (l === 1) {
this.innerText = legendTitle + ': ' + stockVolume;
}
});
}
}
}
}
}

Highcharts: Hide and show legend

I'd like to be able to toggle the visibility of the legend of a chart when the user clicks a button.
I've tried hiding the legend using the undocumented destroy() method, however when I try to re-render the legend and it's items, the items appear in the top left of the chart instead of within the legend. The items also don't seem to have any of their event handlers attached (clicking on an item no longer toggles a series).
Is there a better way to do this? I have to support both SVG and VML implementations, so am looking for a solution that would address both.
JSFiddle Example
$('#updateLegend').on('click', function (e) {
var enable = !chart.options.legend.enabled;
chart.options.legend.enabled = enable;
if (!enable) {
chart.legend.destroy(); //"hide" legend
} else {
var allItems = chart.legend.allItems;
//add legend items back to chart
for (var i = 0; i < allItems.length; i++) {
var item = allItems[i];
item.legendItem.add();
item.legendLine.add();
item.legendSymbol.add();
}
//re-render the legend
chart.legend.render();
}
});

In case when you destroy legend, then you need to generate full legend. Simpler solution is use hide() / show() function for elements.
http://jsfiddle.net/sbochan/3Bh7b/1/
$('#updateLegend').click(function (e) {
var legend = chart.legend;
if(legend.display) {
legend.group.hide();
legend.box.hide();
legend.display = false;
} else {
legend.group.show();
legend.box.show();
legend.display = true;
}
});

Here is an interesting solution I came up with - works for Highcharts3 and Highstocks1.3
https://bitbucket.org/jkowalleck/highcharts-legendextension
All you have to do is to add the HighchartsExtension I wrote to your HTML page, and you get 3 new functions added to the Chart:
myChart.legendHide() ,
myChart.legendShow() and
myChart.legendToggle()
See the examples:
in Highcharts with floating legend: http://jsfiddle.net/P2g6H/
in Highstocks with static legend: http://jsfiddle.net/ps6Pd/

As simple as
myChartObject.legend.update({
enabled:true
});

A fairly simple way to make this is to loop over the series and update them to not show in legend. This allows you to animate in and out of showing the legend and utilize the entire container space, as the methods are built in.
For example, toggling legend items would look like this:
$('#toggleButton').click(function() {
for(i in chart.series)
chart.series[i].update({ showInLegend: chart.series[i].options.showInLegend == null ? false : !chart.series[i].options.showInLegend }, false);
chart.redraw();
});
See this JSFiddle demonstration for toggle, show and hide using buttons.

Update a code little bit of selected answer. Now it will increase the space when show/hide legend.
$('#updateLegend').click(function (e) {
var legend = chart.legend;
if(legend.display) {
legend.group.hide();
legend.box.hide();
legend.display = false;
} else {
legend.group.show();
legend.box.show();
legend.display = true;
}
var series = chart.series[0];
$(chart.series).each(function(){
this.setVisible(true, false);
});
chart.redraw();
});

So far only working solution in the world:
for (i = 0; i < chart.series.length; i++)
chart.series[i].options.showInLegend = true;
chart.series[0].setData(chart.series[0].data);
Rendering manually doesn't work (hiding legend.box etc, always if there are multiple pages in legend, then browser button stays).
setData calls internal renderer which acts quite good and does all what is needed.
Hmm, maybe in the end you can do this:
chart.setSize(
chartWidth,
chartHeight+chart.legend.fullHeight,
false
);

Highcharts - Adding tooltip to ONLY certain dynamically added series

Using highcharts, I am adding multiple series to an exist chart. When adding the series I need to be able to set tooltip on or off depending on the series added.
Here is where I am at:
widget.chart.addSeries({
data: newSeries,
color: color,
tooltip: {
enabled: true,
formatter: function() {
return 'test';
}
}
});

Try this.
Inside chart options.
tooltip: {
formatter: function() {
var text = false;
if(this.series.name == "GOOG") {
// just an example of serie name
// you can use index or other data too
text = 'test';
}
return text;
}
}
demo