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Vaadin Charts - Elements API - Basic Use
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Basic Use

The vaadin-<type>-chart is a regular web component, which you can add to a web page.

You can load the chart in 'header' and then use it in the 'body'. A chart has a height of 400 pixels and takes full width by default. Anyway the chart will adapt its size to its container element size if that has the size specified.

Web Components:

<!DOCTYPE html>
<html>
<head>
  <link rel="import" href="bower_components/vaadin-charts/vaadin-bar-chart.html">
</head>
<body>
  <div style="width:400px;height:300px">
    <vaadin-bar-chart>
      ...
    </vaadin-bar-chart>
  </div>
</body>
</html>

The chart types are described in Chart Types. The main parts of a chart are illustrated in Chart Elements.

charts elements lo
Figure 1. Chart Elements

To actually display something in a chart, you typically need to configure the following aspects:

  • Basic chart configuration

  • Configure plot options for the chart type

  • Configure one or more data series to display

  • Configure axes

The plot options can be configured for each data series individually, or for different chart types in mixed-type charts.

Basic Chart Configuration

After adding a chart web component to your html page, you need to configure it further. At the very least, you need to specify the data series to be displayed in the configuration.

The chart-specific properties can be changed by adding <property-name> tags into the chart. Here we add title and subtitle to the chart. By convention, title should be used, but it is a reserved tag name in HTML and does not allow child elements. In Vaadin Charts, a chart- prefix is added to fix this kind of issues. So, instead of using reserved tags, area, frame, style, and title, use the following elements: chart-area, chart-frame, chart-style, and chart-title.

<vaadin-bar-chart>
  <chart-title>Planets</chart-title>
  <subtitle>The bigger they are the harder they pull</subtitle>
  ...
</vaadin-bar-chart>

The configuration properties are described in more detail in Chart Configuration.

Plot Options

Many chart settings can be configured in the plot options of the chart or data series. Some of the options are chart type specific, as described later for each chart type, while many are shared.

For example, for line charts, you could disable the point markers as follows:

<plot-options>
  <line>
    <marker enabled="false"></marker>
  </line>
</plot-options>

You can set the plot options for the entire chart or for each data series separately, allowing also mixed-type charts, as described in Mixed Type Charts.

The shared plot options are described in Plot Options.

Chart Data Series

The data displayed in a chart is stored as data-series elements.

<data-series name="Diameter">
  <data>
    4900, 12100, 12800, 6800,
    143000, 125000, 51100, 49500
  </data>
</data-series>

Data point features, such as color and size, can be defined inside the data-series element. The data series configuration is described in more detail in Chart Data.

Axis Configuration

One of the most common tasks for charts is customizing its axes. At the least, you usually want to set the axis titles. Usually you also want to specify labels for data values in the axes.

When an axis is categorical rather than numeric, you can define category labels for the items. They must be in the same order and the same number as you have values in your data series.

<x-axis>
  <chart-title>Planet</chart-title>
  <categories>Mercury, Venus, Earth, Mars,
              Jupiter, Saturn, Uranus, Neptune</categories>
</x-axis>

Formatting of numeric labels can be done with format attribute which is a string where '{value}' will be replaced by the actual y-label value.

<y-axis>
  <chart-title>Diameter</chart-title>
  <labels format = "{value} Mm">
    <step>2</step>
  </labels>
</y-axis>

More complex formatting, needs to be done using formatter which is a JavaScript function to format the label.

<y-axis>
  <chart-title>Diameter</chart-title>
  <labels formatter = "function () { return this.value / 1000 + 'Mm';}">
    <step>2</step>
  </labels>
</y-axis>

Displaying Multiple Series

The simplest data, which we saw in the examples earlier in this chapter, is one-dimensional and can be represented with a single data series. Most chart types support multiple data series, which are used for representing two-dimensional data. For example, in line charts, you can have multiple lines and in column charts the columns for different series are grouped by category. Different chart types can offer alternative display modes, such as stacked columns. The legend displays the symbols for each series.

<!-- The data Source:
V. Maijala, H. Norberg, J. Kumpula, M. Nieminen
Calf production and mortality in the Finnish
reindeer herding area. 2002. -->
<data-series name="Bear">
  <data>8, 30, 37, 13, 3</data>
</data-series>
<data-series name="Wolf">
  <data>0, 1, 0, 23, 10</data>
</data-series>
<data-series name="Wolverine">
  <data>7, 30, 22, 4, 9</data>
</data-series>
<data-series name="Lynx">
  <data>0, 2, 2, 1, 0</data>
</data-series>

The result for both regular and stacked column chart is shown in Multiple Series in a Chart. Stacking is enabled with the columns plot-options property stacking.

<plot-options>
  <column>
    <stacking>normal</stacking>
  </column>
</plot-options>
charts twodimensional
Figure 2. Multiple Series in a Chart

Mixed Type Charts

You can enable mixed charts by setting the chart type in the 'data-series' element, which overrides the default chart type of vaadin-<type>-chart element. You can also make color and other settings for the series in the plot options.

For example, to get a line chart, you need to use type line.

<data-series name="Bear">
  <type>column</type>
  <color>blue</color>
  <data>8, 30, 37, 13, 3</data>
</data-series>
<data-series name="Wolf">
  <type>line</type>
  <color>red</color>
  <data>0, 1, 0, 23, 10</data>
</data-series>

In the above case, where we set the chart type for each series, the overall chart type is irrelevant. As long as, it does not change the order of the axis like 'bar' chart would do.

3D Charts

Most chart types can be made 3-dimensional by adding 3D options to the chart. You can rotate the charts, set up the view distance, and define the thickness of the chart features, among other things. You can also set up a 3D axis frame around a chart.

charts 3d pie
Figure 3. 3D Charts

3D Options

3D view has to be enabled in the options3d configuration, along with other parameters. Minimally, to have some 3D effect, you need to rotate the chart according to the alpha and beta parameters.

Let us consider a basic scatter chart for an example. The basic configuration for scatter charts is described elsewhere, but let us look how to make it 3D.

<vaadin-scatter-chart>
  ...
  <chart>
    <options3d enabled="true"
               alpha=10
               beta=30
               depth=300
               view-distance=100>
  </chart>
  ...
</vaadin-scatter-chart>

The 3D options are as follows:

enabled

Whether 3D plot is enabled. Default is false.

alpha

The vertical tilt (pitch) in degrees.

beta

The horizontal tilt (yaw) in degrees.

depth

Depth of the third (Z) axis in pixel units. Default is 100.

chart-frame

Defines the 3D frame, which consists of a back, bottom, and side panels that display the chart grid.

<chart-frame>
  <back size="1" color="#F5F5DC"></back>
</chart-frame>
view-distance

View distance for creating perspective distortion. Default is 100.

3D Plot Options

The above sets up the general 3D view, but you also need to configure the 3D properties of the actual chart type. The 3D plot options are chart type specific. For example, a pie has 'depth' (or thickness), which you can configure as follows:

<plot-options>
  <pie>
    <depth>45</depth> <!-- Our pie is quite thick -->
  </pie>
</plot-options>

3D Data

For some chart types, such as pies and columns, the 3D view is merely a visual representation for one- or two-dimensional data. Some chart types, such as scatter charts, also feature a third, 'depth axis' for data points. That third axis is called a Z axis.

Such data points can be given as arrays of three elements.

<data-series name="3D data">
  <color-by-point>true</color-by-point>
  <data>
    [0.0, 0.0, 0.0],
    [1.0, 0.0, 0.0],
    [0.0, 1.0, 0.0],
    [0.0, 0.0, 1.0],
    [-1.0, 0.0, 0.0],
    [0.0, -1.0, 0.0],
    [0.0, 0.0, -1.0]
  </data>
</data-series>

Alternatively, the data points can be given as objects which have 'x', 'y' and 'z' properties.

<data-series name="3D data">
  <color-by-point>true</color-by-point>
  <data>
    {x: 0.0, y: 0.0, z:0.0},
    {x:1.0, y:0.0, z:0.0},
    {x:0.0, y:1.0, z:0.0},
    {x:0.0, y:0.0, z:1.0},
    {x:-1.0, y:0.0, z:0.0},
    {x:0.0, y:-1.0, z:0.0},
    {x:0.0, y:0.0, z:-1.0}
  </data>
</data-series>

Above, we defined 7 orthogonal data points in the 2x2x2 cube centerd in origo. The result is illustrated in 3D Scatter Chart.

charts 3d scatter
Figure 4. 3D Scatter Chart

Distance Fade

To add a bit more 3D effect, you can do some tricks, such as calculate the distance of the data points from a viewpoint and set the marker size and color according to the distance. To add custom JavaScript to do this, dom-bind element can be used. More information about binding data to a chart can be found here.

<template id="fade" is="dom-bind">
  ...
  <vaadin-scatter-chart id="fadeChart">
    ...
    <data-series name="Data" data="[[distanceFadeData]]">
    </data-series>
  </vaadin-scatter-chart>
</template>
<script>
  var fade = document.querySelector('#fade');
  fade.addEventListener('dom-change', function() {
        var viewX = 0; var viewY = 0; var viewZ = 0;
        calculateViewPoint();

        fade.distanceFadeData =  [createPoint(0.0, 0.0, 0.0),
                                  createPoint(1.0, 0.0, 0.0),
                                  createPoint(0.0, 1.0, 0.0),
                                  createPoint(0.0, 0.0, 1.0),
                                  createPoint(-1.0, 0.0, 0.0),
                                  createPoint(0.0, -1.0, 0.0),
                                  createPoint(0.0, 0.0, -1.0)];

        function calculateViewPoint() {
          var viewDist = 2;
          var fadeChart = document.querySelector('#fadeChart');
          var alpha = fadeChart.chart.options.chart.options3d.alpha;
          var beta = fadeChart.chart.options.chart.options3d.beta;
          var theta = alpha * Math.PI / 180;
          var phi = beta * Math.PI / 180;
          viewX = viewDist * Math.sin(theta) * Math.cos(phi);
          viewY = viewDist * Math.sin(theta) * Math.sin(phi);
          viewZ = - viewDist * Math.cos(theta);
        }

        function createPoint(x, y, z) {
            var distance = calculateDistance(x,y,z);
            var grayness = parseInt(distance*75);
            return {x: x, y: y, z: z,
                    radius: 1+ 10/distance,
                    color: createColor(grayness)};
        }

        function createColor(color) {
            return "rgb("+color+","+color+","+color+")";
        }

        function calculateDistance(x, y, z) {
            return Math.sqrt(Math.pow(viewX - x, 2) +
                             Math.pow(viewY - y, 2) +
                             Math.pow(viewZ - z, 2));
        }
  });
</script>

Note that here the view distance is in the scale of the data coordinates, while the distance defined in the 3D options has different definition and scaling. With the above settings, which are somewhat exaggerated to illustrate the effect, the result is shown in 3D Distance Fade.

charts 3d fade
Figure 5. 3D Distance Fade