flex line chart with variable colored line

Question

Ive got a rather simple need to create a line chart. The data that I would like to chart is based on a single daily datapoint. xml example of data:

<?xml version="1.0"?>
<dataset>
    <data>
        <date>01/14/2013</date>
        <number>80.6</number>
        <indication>G</indication>
    </data>
    <data>
        <date>01/15/2013</date>
        <number>74.6</number>
        <indication>A</indication>
    </data>
    <data>
        <date>01/21/2013</date>
        <number>79.4</number>
        <indication>G</indication>
    </data>
    <data>
        <date>01/22/2013</date>
        <number>67.7</number>
        <indication>A</indication>
    </data>
</dataset>

The trick is that I want to alter the plotted line color based on the value in indication.

In other words if my first point is on 01/14/2013 I want the color of the line between that point and the next to be based on the indication so with the example data above it would be amber. Then from the second point to the 3rd green and from the thirs to the fourth amber again.

I really like the amstock charts but they seem to be lacking this functionality.

Has anyone seen any components capable of this or have ideas how I could do it with default flex 4.6 components?

Answer 1

I have an idea, i hope it will help you.

You can process your dataset and form a new one from it, so that each two points represent a single datasource for one line chart segment.

Then you go through all your segments and add them separate to the chart.

You need two classes to save informations about "points" and "parts"

//Part.as

public class Part
{
    public var col:Number;
    public var punkts:ArrayCollection;
}

//Punkt.as

public class Punkt
{
    public var date:String;
    public var number:Number;

    public function Punkt(date:String, number:Number)
    {
        this.date = date;
        this.number = number;
    }
}

//here is your application

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
           xmlns:s="library://ns.adobe.com/flex/spark" 
           xmlns:mx="library://ns.adobe.com/flex/mx" 
           minWidth="955" minHeight="600" 
           creationComplete="init()">

<fx:Declarations>
    <fx:Model id="myData">
        <dataset>
            <data>
                <date>01/14/2013</date>
                <number>80.6</number>
                <indication>G</indication>
            </data>
            <data>
                <date>01/15/2013</date>
                <number>74.6</number>
                <indication>A</indication>
            </data>
            <data>
                <date>01/21/2013</date>
                <number>79.4</number>
                <indication>G</indication>
            </data>
            <data>
                <date>01/22/2013</date>
                <number>67.7</number>
                <indication>G</indication>
            </data>
            <data>
                <date>01/24/2013</date>
                <number>47.7</number>
                <indication>A</indication>
            </data>
            <data>
                <date>01/25/2013</date>
                <number>87.7</number>
                <indication>G</indication>
            </data>
        </dataset>
    </fx:Model>
</fx:Declarations>

<fx:Script>
    <![CDATA[
        import com.Part;
        import com.Punkt;

        import mx.charts.series.LineSeries;
        import mx.collections.ArrayCollection;
        import mx.graphics.SolidColorStroke;
        import mx.graphics.Stroke;
        import mx.utils.ObjectProxy;

        [Bindable]private var xAxis:ArrayCollection = new ArrayCollection();
        [Bindable]private var dp:ArrayCollection = new ArrayCollection();

        private function init():void
        {
            var prevCol:Number = 0x000000;

            var len:int = myData.data.length;
            var item:ObjectProxy;
            var i:int;

            for (i = 0; i < len; i++)
            {
                item = myData.data[i];
                xAxis.addItem(item.date);
            }

            for (i = 0; i < len - 1; i++)
            {
                item = myData.data[i];
                var part:Part = new Part();

                switch (item.indication)
                {
                    case "A":
                        part.col = 0xe48701;
                        break;
                    case "G":
                        part.col = 0xa5bc4e;
                        break;
                }

                part.punkts = new ArrayCollection();

                part.punkts.addItem(new Punkt(item.date, item.number));

                item = myData.data[i + 1];
                part.punkts.addItem(new Punkt(item.date, item.number));

                dp.addItem(part);
            }

            var mySeries:Array=new Array();

            for each (var part:Part in dp)
            {
                var lineSeries:LineSeries = new LineSeries();
                lineSeries.dataProvider = part.punkts;
                lineSeries.xField = "date";
                lineSeries.yField = "number";

                lineSeries.setStyle('lineStroke', new SolidColorStroke(part.col, 3, 1));

                mySeries.push(lineSeries);
            }

            lc.series = mySeries;
        }

    ]]>
</fx:Script>

<mx:LineChart id="lc" x="184" y="55">
    <mx:horizontalAxis>
        <mx:CategoryAxis dataProvider="{xAxis}"/>
    </mx:horizontalAxis>
</mx:LineChart>

</s:Application>