reading-notes

Class-12 reading Summary

Charts are far better for displaying data visually than tables and have the added benefit that no one is ever going to press-gang them into use as a layout tool. They’re easier to look at and convey data quickly, but they’re not always easy to create.

A great way to get started with charts is with Chart.js, a JavaScript plugin that uses HTML5’s canvas element to draw the graph onto the page. It’s a well documented plugin that makes using all kinds of bar charts, line charts, pie charts and more, incredibly easy.

To see how to use chart.js we’re going to create a set of 3 graphs; one will show the number of buyers a fictional product has over the course of 6 months, this will be a line chart; the second will show which countries the customers come from, this will be the pie chart; finally we’ll use a bar chart to show profit over the period.

It’s easy to get started with Chart.js. All that’s required is the script included in your page along with a single <canvas> node to render the chart.

In this example, we create a bar chart for a single dataset and render that in our page. You can see all the ways to use Chart.js in the usage documentation.

<canvas id="myChart" width="400" height="400"></canvas>
<script>
var ctx = document.getElementById('myChart').getContext('2d');
var 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: {
            yAxes: [{
                ticks: {
                    beginAtZero: true
                }
            }]
        }
    }
});
</script>