How to build any Ionic Chart or visualization in 4 steps (2024)

Step 3: Best Ionic chart libraries

After analyzing the different Ionic charting libraries available. I choose my top three based on both SVG and Canvas, to provide a wide range of options for the different use cases that may arise when building an Ionic app.

Without further ado, here are our top three picks in order of preference:

Charting LibraryTechnologyHealthConfiguration
ngx-echartsBased on EChartsCanvasUp to dateWide optionsEasy (*1)
ng2-chartsBased on Chart.jsCanvasUp to dateLess optionsEasy (*1)
ngx-chartsBased on D3.jsSVGUp to dateWide optionsDifficult (*2)

(*1) Through JSON configuration object
(*2) Through declarative inputs and SVG elements

If you want to read the in depth analysis where I explore the characteristics of each charting library and both the pros and cons, I suggest you read my previous post about Building Charts with Angular.

Building a line chart with Ionic

I will be building one basic yet complete Ionic chart using the top three Ionic charting libraries.

The chart example features a line chart with different data sets, and some Ionic controls to interact with the chart. These controls can be used to filter data, toggle the different data sets shown in the chart and dynamically change some properties of the visualization.

By default almost every charting library comes with built-in controls to interact with the chart. This is not bad at all, but when designing a mobile app you can greatly improve the user experience if you own the different pieces of the UI.

That’s why I believe it’s important to show you how to interact with the chart using Ionic controls instead of the ones built-inside the charting library.

Ionic charts using ngx-echarts

ngx-echarts is an open source Angular library built on top of ECharts. The customization possibilities and the documentation are the two aspects I like the most about this Angular charting library. You can define a wide set of configuration options to customize every single detail of the chart.

On top of that, it provides a beautiful API to interact with the chart instance. Enabling you to build more advanced visualizations.

Also, its documentation is super complete, featuring lots of interactive examples with code playgrounds included.

The configuration for this charting library is straightforward, just add a JSON configuration object to the Ionic page component with your desired options. There’s also detailed documentation with all the different configuration options available.

lineChartOptions: EChartsOption = { tooltip : { trigger: 'item', formatter: '{c}' }, xAxis: { type: 'category', axisLine: { show: false }, axisTick: { show: false }, data: CHART_LABELS, splitLine: { show: false } }, yAxis: { type: 'value', axisTick: { show: false }, splitNumber: 4, axisLine: { show: false } }, grid: { left: '10%', right: '0%' }, series: [ { id: 'earnings', name: 'Earnings', type: 'line' }, { id: 'revenue', name: 'Revenue', type: 'line', lineStyle: { color: '#CCC', type: 'dashed' } } ]};

Then the markup in your HTML file would be as simple as:

<div echarts [options]="lineChartOptions" (chartInit)="onChartInit($event)"></div>

For the ECharts line chart, the data has to be in this format under the series property of the configurations object:

lineChartOptions: EChartsOption = { … series: [ { id: 'earnings', name: 'Earnings', data: [680, 932, 901, 934, 1290, 1330, 1320], type: 'line' }, { id: 'revenue', name: 'Revenue', data: [620, 999, 1003, 1200, 1100, 1200, 1500], type: 'line', lineStyle: { color: '#CCC', type: 'dashed' } } ]};

I typically hard code some dummy data while I’m working on the visualization. Once the UI and user experience is polished, I start working on the services to fetch and format the data correctly.

How to build any Ionic Chart or visualization in 4 steps (1)

Ionic line chart using ngx-echarts

Ionic charts using ng2-charts

ng2-charts is also an open-source Angular library, but it's based on Chart.js. The library is maintained by the Valor Team (if you are an Angular Bootstrap developer, you may know them for their popular ngx-bootstrap library).

This Angular charting library features one directive (baseChart) that can be instantiated with any of the eight types of built-in charts: line chart, bar chart, radar chart, pie chart, polar area chart, doughnut chart, bubble chart and scatter plot.

The baseChart directive provides some properties to configure and customize the chart. It's worth mentioning that these properties are constrained by the configuration options provided by Charts.js (which are limited compared to ECharts).

In the Ionic page component, you need to set up some JavaScript objects for the different elements of the chart (labels, legend, data sets, etc.).

public lineChartOptions: ChartConfiguration['options'] = { responsive: true, layout: { padding: { top: 0, left: 0, bottom: 0, right: 0 } }, scales: { x: { axis: 'x', grid: { drawBorder: false, display: false }, ticks: { display: true } }, y: { axis: 'y', min: 0, grid: { drawBorder: false, display: true, drawTicks: false }, ticks: { padding: 10 } } }, plugins: { legend: { display: false } }};public lineChartType: ChartType = 'line';

Then, you can reference those objects in the markup like this:

<canvas baseChart [data]="lineChartData" [options]="lineChartOptions" [type]="lineChartType"></canvas>

In this case, for the line chart we need to set our data with this format:

this.lineChartData = { labels: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'], datasets: [ { label: 'Earnings', data: [980, 232, 601, 434, 1090, 1230, 1720], borderColor: '#035388', backgroundColor: 'rgba(3,83,136,0.4)' }, { label: 'Revenue', data: [120, 699, 1203, 1700, 1200, 1100, 1900] } ]};
How to build any Ionic Chart or visualization in 4 steps (2)

Ionic line chart using ng2-charts

Ionic charts using ngx-charts

Like the previous ones, the ngx-charts charting library is also open source. But, in contrast to the previous ones, it has a declarative approach and is based on SVG elements and the powerful D3.js visualization library.

Specifically, it uses Angular to render and animate the SVG elements with all of its binding and speed goodness, and uses D3.js for the excellent math functions, scales, axis and shape generators, etc.

This leaves out of the equation the possibility to render D3.js visualizations using canvas. ngx-charts is all about SVG.

The bright side of having Angular do all the SVG rendering is that it opens endless possibilities the Angular platform provides such as Ahead Of Time compilation, Server Side Rendering, etc.

In terms of customization, ngx-charts provides great flexibility as it exports all the components and helpers used as building blocks for the charts. Things like legends, axes, dimension helpers, gradients, shapes, can be directly imported into your application and used in your angular components. This allows you to combine them and build custom charts that implement use cases that the default library's charts do not support.

I have to say that although this level of customization is great, you still need to deep dive into the different chart primitives and interact directly with the SVG nodes (take for example this custom chart source code). This is considerably harder to do than customizing a configuration JSON object like we saw in the previous two charting libraries.

This charting library also provides easy to customize components for the most popular chart types (line charts, bar charts, pie charts, heat maps, polar/radar charts, gauge charts, and bubble charts among others).

This way you don’t have to struggle with the different chart primitives (legends, axes, gradients) yourself. You can set the different configuration options using a JSON object like this:

colorScheme = { domain: ['#035388', '#40c3f7', '#b3ecff', '#52606d', '#127fbf', '#9aa5b1']};lineChartOptions = { showXAxis: true, showYAxis: true, showLegend: false, showGridLines: true, showXAxisLabel: false, showYAxisLabel: false, legendPosition: 'right', autoScale: false, roundDomains: true};

And the markup in your HTML file would be as simple as:

<ngx-charts-line-chart [scheme]="colorScheme" [results]="lineChartData" [legendPosition]="lineChartOptions.legendPosition" [xAxis]="lineChartOptions.showXAxis" [yAxis]="lineChartOptions.showYAxis" [legend]="lineChartOptions.showLegend" [showXAxisLabel]="lineChartOptions.showXAxisLabel" [showYAxisLabel]="lineChartOptions.showYAxisLabel" [roundDomains]="lineChartOptions.roundDomains" [autoScale]="lineChartOptions.autoScale" [curve]="lineChartOptions.curve" [showGridLines]="lineChartOptions.showGridLines"></ngx-charts-line-chart>

In this case, the data for the line chart must follow this format:

lineChartData = [ { name: 'Earnings', series: [ { value: 680, name: 'Mon' }, { value: 932, name: 'Tue' }, { value: 901, name: 'Wed' }, { value: 934, name: 'Thu' }, { value: 1290, name: 'Fri' }, { value: 1330, name: 'Sat' }, { value: 1320, name: 'Sun' } ] }, { name: 'Revenue', series: [ { value: 620, name: 'Mon' }, { value: 999, name: 'Tue' }, { value: 1003, name: 'Wed' }, { value: 1200, name: 'Thu' }, { value: 1100, name: 'Fri' }, { value: 1200, name: 'Sat' }, { value: 1500, name: 'Sun' } ] }];
How to build any Ionic Chart or visualization in 4 steps (3)

Ionic line chart using ngx-charts

Using Ionic controls to interact with the charts

As mentioned before, all the three charting libraries use either JavaScript or JSON objects to configure and handle the data displayed in the visualization.

We are going to add some Ionic controls to update the data displayed in the visualization.

For this example, I created a simple service that fetches and filters the data, and also formats the data to match the requirements of the three different Ionic charting libraries. For simplicity, I will be using a file with hard-coded dummy data as the data source.

The HTML for the Ionic form controls is the same in all three charting examples:

<form [formGroup]="chartControlsGroup"> <ion-list> <ion-item> <ion-label>Earnings</ion-label> <ion-checkbox slot="end" formControlName="earningsData"></ion-checkbox> </ion-item> <ion-item> <ion-label>Revenue</ion-label> <ion-checkbox slot="end" formControlName="revenueData"></ion-checkbox> </ion-item> <ion-item> <ion-label>Smooth</ion-label> <ion-toggle formControlName="smoothLine"></ion-toggle> </ion-item> <ion-item> <ion-label>Data period</ion-label> <ion-select formControlName="dataPeriod" placeholder="Select a period of time for the data"> <ion-select-option value="lastWeek">Last Week</ion-select-option> <ion-select-option value="thisWeek">This Week</ion-select-option> </ion-select> </ion-item> </ion-list></form>

These controls enable us to toggle the different data sets (Earnings, Revenue), change some properties of the chart (line style: smooth or plain) and filter the data shown in the chart by time period (this week, last week).

How to build any Ionic Chart or visualization in 4 steps (4)

Ionic controls to interact with the charts

I also added a mechanism to listen to changes in the form controls values. This will enable us to dynamically update the chart accordingly.

While the mechanism works the same way in all three examples, the implementation varies a little because each charting library has different ways to update the data shown in the visualization.

Update the line style property of the chart based on the toggle control

this.chartControlsGroup.get('smoothLine').valueChanges.subscribe(isSmooth => { console.log('smoothLine', isSmooth); …});

Update the chart data based on the selected date period and the values of the other controls:

this.chartControlsGroup.get('dataPeriod').valueChanges.subscribe(dataPeriod => { console.log('dataPeriod', dataPeriod); // ? Check what series we should show in the chart const showEarnings = this.chartControlsGroup.get('earningsData').value; const showRevenue = this.chartControlsGroup.get('revenueData').value; const dataCategory = (showEarnings & showRevenue) ? 'all' : (showEarnings ? 'earnings' : (showRevenue ? 'revenue' : null)); if (dataCategory !== null) { const chartData = this.chartsDataService.getData(dataPeriod, dataCategory, 'ngx-echarts'); … }});

And finally toggle and update the data of the different data sets:

this.chartControlsGroup.get('earningsData').valueChanges.subscribe(toggleEarningsData => { console.log('toggleEarningsData', toggleEarningsData); // ? Check what period of data we should show in the chart const dataPeriod = this.chartControlsGroup.get('dataPeriod').value; const earningsData = (toggleEarningsData) ? this.chartsDataService.getData(dataPeriod, 'earnings', 'ngx-echarts').data : [];});this.chartControlsGroup.get('revenueData').valueChanges.subscribe(toggleRevenueData => { console.log('toggleRevenueData', toggleRevenueData); // ? Check what period of data we should show in the chart const dataPeriod = this.chartControlsGroup.get('dataPeriod').value; const revenueData = (toggleRevenueData) ? this.chartsDataService.getData(dataPeriod, 'revenue', 'ngx-echarts').data : [];});

Use your imagination to combine different form controls to filter the data and elements shown in the chart.

Different mechanisms to update the charts

As I mentioned before, each charting library has its own api and methods to update configuration options and data.

To be completely honest with you, this was one of the trickiest tasks I faced when building this demo and tutorial.

Updating ngx-echarts Ionic charts

While you can re-assign the JavaScript options object (lineChartOptions: EChartsOption) to update the chart, the ngx-echarts library has a specific method to update properties.

We first need to get the instance of the chart and then call the setOptions() method when needed.

Get ECharts instance:

echartsInstance: ECharts;onChartInit(chart: ECharts) { this.echartsInstance = chart;}

Once we have the chart instance we can safely update the options configuration:

this.echartsInstance.setOption({ series: [ { id: 'earnings', data: [680, 932, 901, 934, 1290, 1330, 1320] } ]});

Updating ng2-charts Ionic charts

The ng2-charts library does not provide a direct way to update configuration options or data. We have to rely on updating the JavaScript objects references (lineChartData: ChartData<'line'> and lineChartOptions: ChartConfiguration['options']) and then call the update method of the chart instance.

So, first we need to get the instance of the chart using the Angular ViewChild:

@ViewChild(BaseChartDirective) chartInstance?: BaseChartDirective;

Then, every time we update the data, we need to call the chart instance update() method:

this.lineChartData.datasets[1].data = [620, 999, 1003, 1200, 1100, 1200, 1500];this.chartInstance?.update();

Chart options can be changed without calling the update method:

this.lineChartOptions = { ...this.lineChartOptions, elements: { line: { tension: isSmooth ? 0.4 : 0 } },};

Additionally, to hide data sets, we can call the hideDataset() method instead of updating the data set with an empty Array:

this.chartInstance?.hideDataset(1, true);

Updating ngx-charts Ionic charts

ngx-charts handles all the rendering of the SVG elements through Angular itself. Thus you need to update the different javascript objects (lineChartOptions and lineChartData) in order to see the changes in the visualization.

Easily override the chart options object using the spread operator:

this.lineChartOptions = { ...this.lineChartOptions, curve: isSmooth ? curveNatural : curveLinear};

Use the same technique to update all the data sets or just one in particular:

this.lineChartData = this.chartsDataService.getData(dataPeriod, dataCategory, 'ngx-charts');this.lineChartData[0] = {...this.lineChartData[0], series: earningsData};
How to build any Ionic Chart or visualization in 4 steps (2024)
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