inst/htmlwidgets/lib/chartjs/docs/00-Getting-Started.md

In shaneporter/radarchart: Radar chart using htmlwidgets.

title: Getting started anchor: getting-started

Include Chart.js

First we need to include the Chart.js library on the page. The library occupies a global variable of Chart.

<script src="Chart.js"></script>

Alternatively, if you're using an AMD loader for JavaScript modules, that is also supported in the Chart.js core. Please note: the library will still occupy a global variable of Chart, even if it detects define and define.amd. If this is a problem, you can call noConflict to restore the global Chart variable to it's previous owner.

// Using requirejs
require(['path/to/Chartjs'], function(Chart){
    // Use Chart.js as normal here.

    // Chart.noConflict restores the Chart global variable to it's previous owner
    // The function returns what was previously Chart, allowing you to reassign.
    var Chartjs = Chart.noConflict();

});

You can also grab Chart.js using bower:

bower install Chart.js --save

Creating a chart

To create a chart, we need to instantiate the Chart class. To do this, we need to pass in the 2d context of where we want to draw the chart. Here's an example.

<canvas id="myChart" width="400" height="400"></canvas>

// Get the context of the canvas element we want to select
var ctx = document.getElementById("myChart").getContext("2d");
var myNewChart = new Chart(ctx).PolarArea(data);

We can also get the context of our canvas with jQuery. To do this, we need to get the DOM node out of the jQuery collection, and call the getContext("2d") method on that.

// Get context with jQuery - using jQuery's .get() method.
var ctx = $("#myChart").get(0).getContext("2d");
// This will get the first returned node in the jQuery collection.
var myNewChart = new Chart(ctx);

After we've instantiated the Chart class on the canvas we want to draw on, Chart.js will handle the scaling for retina displays.

With the Chart class set up, we can go on to create one of the charts Chart.js has available. In the example below, we would be drawing a Polar area chart.

new Chart(ctx).PolarArea(data, options);

We call a method of the name of the chart we want to create. We pass in the data for that chart type, and the options for that chart as parameters. Chart.js will merge the global defaults with chart type specific defaults, then merge any options passed in as a second argument after data.

Global chart configuration

This concept was introduced in Chart.js 1.0 to keep configuration DRY, and allow for changing options globally across chart types, avoiding the need to specify options for each instance, or the default for a particular chart type.

Chart.defaults.global = {
    // Boolean - Whether to animate the chart
    animation: true,

    // Number - Number of animation steps
    animationSteps: 60,

    // String - Animation easing effect
    animationEasing: "easeOutQuart",

    // Boolean - If we should show the scale at all
    showScale: true,

    // Boolean - If we want to override with a hard coded scale
    scaleOverride: false,

    // ** Required if scaleOverride is true **
    // Number - The number of steps in a hard coded scale
    scaleSteps: null,
    // Number - The value jump in the hard coded scale
    scaleStepWidth: null,
    // Number - The scale starting value
    scaleStartValue: null,

    // String - Colour of the scale line
    scaleLineColor: "rgba(0,0,0,.1)",

    // Number - Pixel width of the scale line
    scaleLineWidth: 1,

    // Boolean - Whether to show labels on the scale
    scaleShowLabels: true,

    // Interpolated JS string - can access value
    scaleLabel: "<%=value%>",

    // Boolean - Whether the scale should stick to integers, not floats even if drawing space is there
    scaleIntegersOnly: true,

    // Boolean - Whether the scale should start at zero, or an order of magnitude down from the lowest value
    scaleBeginAtZero: false,

    // String - Scale label font declaration for the scale label
    scaleFontFamily: "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif",

    // Number - Scale label font size in pixels
    scaleFontSize: 12,

    // String - Scale label font weight style
    scaleFontStyle: "normal",

    // String - Scale label font colour
    scaleFontColor: "#666",

    // Boolean - whether or not the chart should be responsive and resize when the browser does.
    responsive: false,

    // Boolean - whether to maintain the starting aspect ratio or not when responsive, if set to false, will take up entire container
    maintainAspectRatio: true,

    // Boolean - Determines whether to draw tooltips on the canvas or not
    showTooltips: true,

    // Function - Determines whether to execute the customTooltips function instead of drawing the built in tooltips (See [Advanced - External Tooltips](#advanced-usage-custom-tooltips))
    customTooltips: false,

    // Array - Array of string names to attach tooltip events
    tooltipEvents: ["mousemove", "touchstart", "touchmove"],

    // String - Tooltip background colour
    tooltipFillColor: "rgba(0,0,0,0.8)",

    // String - Tooltip label font declaration for the scale label
    tooltipFontFamily: "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif",

    // Number - Tooltip label font size in pixels
    tooltipFontSize: 14,

    // String - Tooltip font weight style
    tooltipFontStyle: "normal",

    // String - Tooltip label font colour
    tooltipFontColor: "#fff",

    // String - Tooltip title font declaration for the scale label
    tooltipTitleFontFamily: "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif",

    // Number - Tooltip title font size in pixels
    tooltipTitleFontSize: 14,

    // String - Tooltip title font weight style
    tooltipTitleFontStyle: "bold",

    // String - Tooltip title font colour
    tooltipTitleFontColor: "#fff",

    // Number - pixel width of padding around tooltip text
    tooltipYPadding: 6,

    // Number - pixel width of padding around tooltip text
    tooltipXPadding: 6,

    // Number - Size of the caret on the tooltip
    tooltipCaretSize: 8,

    // Number - Pixel radius of the tooltip border
    tooltipCornerRadius: 6,

    // Number - Pixel offset from point x to tooltip edge
    tooltipXOffset: 10,
    {% raw %}
    // String - Template string for single tooltips
    tooltipTemplate: "<%if (label){%><%=label%>: <%}%><%= value %>",
    {% endraw %}
    // String - Template string for multiple tooltips
    multiTooltipTemplate: "<%= value %>",

    // Function - Will fire on animation progression.
    onAnimationProgress: function(){},

    // Function - Will fire on animation completion.
    onAnimationComplete: function(){}
}

If for example, you wanted all charts created to be responsive, and resize when the browser window does, the following setting can be changed:

Chart.defaults.global.responsive = true;

Now, every time we create a chart, options.responsive will be true.

shaneporter/radarchart documentation built on May 29, 2019, 8:07 p.m.