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Add Annotations

Annotations are graphical elements (different types of shapes, custom text, and so on) that you can render on your chart to make it more informative, while making it visually appealing.

In this article we'll create a Spline chart and add annotations using FusionCharts Rails gem wrapper. A spline chart using annotations to highlight a particular anchor along with text is shown below:

FusionCharts will load here..
{
    "chart": {
        "caption": "Average Monthly Temperature in Texas",
        "yAxisName": "Average Monthly Temperature",
        "anchorradius": "5",
        "plotToolText": "Average temperature in $label is <b>$dataValue</b>",
        "showHoverEffect": "1",
        "showvalues": "0",
        "numberSuffix": "°C",
        "theme": "fusion",
        "anchorBgColor": "#72D7B2",
        "paletteColors": "#72D7B2"
    },
    "annotations": {
        "groups": [
            {
                "id": "anchor-highlight",
                "items": [
                    {
                        "id": "high-star",
                        "type": "circle",
                        "x": "$dataset.0.set.7.x",
                        "y": "$dataset.0.set.7.y",
                        "radius": "12",
                        "color": "#cc0000",
                        "border": "2",
                        "borderColor": "#0075c2"
                    },
                    {
                        "id": "label",
                        "type": "text",
                        "text": "Hottest Month",
                        "fillcolor": "#0075c2",
                        "rotate": "90",
                        "x": "$dataset.0.set.7.x+75",
                        "y": "$dataset.0.set.7.y-2"
                    }
                ]
            }
        ]
    },
    "data": [
        {
            "label": "Jan",
            "value": "1"
        },
        {
            "label": "Feb",
            "value": "5"
        },
        {
            "label": "Mar",
            "value": "10"
        },
        {
            "label": "Apr",
            "value": "12"
        },
        {
            "label": "May",
            "value": "14"
        },
        {
            "label": "Jun",
            "value": "16"
        },
        {
            "label": "Jul",
            "value": "20"
        },
        {
            "label": "Aug",
            "value": "22"
        },
        {
            "label": "Sep",
            "value": "20"
        },
        {
            "label": "Oct",
            "value": "16"
        },
        {
            "label": "Nov",
            "value": "7"
        },
        {
            "label": "Dec",
            "value": "2"
        }
    ]
}

The code to render the above sample is given below:

<%
    require 'fusioncharts-rails'
    def getChart
        chartData = {
            "chart": {
                "caption": "Average Monthly Temperature in Texas",
                "yAxisName": "Average Monthly Temperature",
                "anchorradius": "5",
                "plotToolText": "Average temperature in $label is <b>$dataValue</b>",
                "showHoverEffect": "1",
                "showvalues": "0",
                "numberSuffix": "°C",
                "theme": "fusion",
                "anchorBgColor": "#72D7B2",
                "paletteColors": "#72D7B2"
            },
            "annotations": {
                "groups": [{
                    "id": "anchor-highlight",
                    "items": [{
                        "id": "high-star",
                        "type": "circle",
                        "x": "$dataset.0.set.7.x",
                        "y": "$dataset.0.set.7.y",
                        "radius": "12",
                        "color": "#cc0000",
                        "border": "2",
                        "borderColor": "#0075c2"
                    }, {
                        "id": "label",
                        "type": "text",
                        "text": "Hottest Month",
                        "fillcolor": "#0075c2",
                        "rotate": "90",
                        "x": "$dataset.0.set.7.x+75",
                        "y": "$dataset.0.set.7.y-2"
                    }]
                }]
            },
            "data": [{
                "label": "Jan",
                "value": "1"
            }, {
                "label": "Feb",
                "value": "5"
            }, {
                "label": "Mar",
                "value": "10"
            }, {
                "label": "Apr",
                "value": "12"
            }, {
                "label": "May",
                "value": "14"
            }, {
                "label": "Jun",
                "value": "16"
            }, {
                "label": "Jul",
                "value": "20"
            }, {
                "label": "Aug",
                "value": "22"
            }, {
                "label": "Sep",
                "value": "20"
            }, {
                "label": "Oct",
                "value": "16"
            }, {
                "label": "Nov",
                "value": "7"
            }, {
                "label": "Dec",
                "value": "2"
            }]
        }

        # Chart rendering 
        chart = Fusioncharts::Chart.new({
            width: "700",
            height: "400",
            type: "spline",
            renderAt: "chartContainer",
            dataSource: chartData
        })
    end
%>

The HTML template of the above sample is shown below:

<div style="width: 100%; display: block;" align="center">
    <div id="chartContainer">
        <%= getChart.render() %>
    </div>
</div>

The above chart has been rendered using the following steps:

  1. Include the necessary libraries and components using require. For example, fusioncharts-rails, fusioncharts, etc

  2. Store the chart data in a JSON object.

  3. Create an annotations object in the chartData, to specify the cosmetics and functionalities of the annotation.

  4. Store the chart configuration in a JSON object. In the JSON object:

    • Set the chart type as spline. Find the complete list of chart types with their respective alias here.
    • Set the width and height of the chart in pixels.
    • Set the container of the chart to chartContainer.
    • Embed the json data as the value of chartData.

  5. Create the <div> element to render the chart using id.