Flex: Inverting LinearAxis values

Question

I have a line chart that is updated every so and so seconds, similar to the one you see in Windows' Task Manager. The chart goes right-to-left, with the most recent data on the right, and going leftwards. How would I invert the values of the X axis so that the lowest value is on the right and the highest on the left? It's a LinearAxis.

I tried making it a CategoryAxis and putting the numbers in manually, but that doesn't work the way it should (the labels are not aligned with the ticks).

Or, is there a way to have the labels in a CategoryAxis align with the ticks?

Answer 1

So I've looked into it an i also can't see a straightforward way of flipping the axis. However i do have a solution that would work perfectly well and is relatively elegant giving the omission of a property to do this for you.

So consider this normal left-to-right line chart (should just be able to copy and paste this into a project to test).

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <![CDATA[          
        import mx.collections.ArrayCollection;

        [Bindable]
        private var timeValue:ArrayCollection = new ArrayCollection( [
            { Time: 0, Value: 18 },
            { Time: 1, Value: 20 },
            { Time: 2, Value: 30 },
            { Time: 3, Value: 35 }, 
            { Time: 4, Value: 35 }, 
            { Time: 5, Value: 32 }, 
            { Time: 6, Value: 40 }, 
            { Time: 7, Value: 62 }, 
            { Time: 8, Value: 80 },
            { Time: 9, Value: 75 },
            { Time: 10, Value: 76 } ]);
        ]]>
    </mx:Script>

    <!-- Define custom colors for use as fills. -->
    <mx:SolidColor id="sc1" color="yellow" alpha=".8"/>

    <!-- Define custom Strokes for the columns. -->
    <mx:Stroke id="s1" color="yellow" weight="2"/>

    <mx:Panel title="ColumnChart and BarChart Controls Example" 
        height="100%" width="100%" layout="horizontal">
        <mx:LineChart id="column" 
            height="100%" 
            width="100%" 
            paddingLeft="5" 
            paddingRight="5" 
            showDataTips="true" 
            dataProvider="{timeValue}" >

            <mx:horizontalAxis>
                <mx:LinearAxis maximum="10" minimum="0"/>
            </mx:horizontalAxis>

            <mx:verticalAxis>
                <mx:LinearAxis maximum="100" minimum="0" />         
            </mx:verticalAxis>

            <mx:series>
                <mx:LineSeries 
                    xField="Time" 
                    yField="Value" 
                    displayName="TimeValue"
                    fill="{sc1}"
                    stroke="{s1}"
                />
            </mx:series>
        </mx:LineChart>

    </mx:Panel>
</mx:Application>

To change this to a right-to-left chart, i do some inverting of the time values to make them negative and then plot them along an axis that uses a negative minimum and zero as the maximum. I also then run a function on the labels to make them positive again to fit the original data source.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <![CDATA[
            import mx.charts.chartClasses.IAxisRenderer;          
            import mx.collections.ArrayCollection;

            [Bindable]
            private var timeValue:ArrayCollection = new ArrayCollection( [
                { Time: 0, Value: 18 },
                { Time: 1, Value: 20 },
                { Time: 2, Value: 30 },
                { Time: 3, Value: 35 }, 
                { Time: 4, Value: 35 }, 
                { Time: 5, Value: 32 }, 
                { Time: 6, Value: 40 }, 
                { Time: 7, Value: 62 }, 
                { Time: 8, Value: 80 },
                { Time: 9, Value: 75 },
                { Time: 10, Value: 76 } ]);

            private function verticalAxisParseFunction(value : Number) : Number
            {
                return value * -1;
            }

            private function horizontalAxisRenderedLabelFunction(axisRenderer:IAxisRenderer, label:String):String
            {
                var labelAsNumber : Number = Number(label);

                if (isNaN(labelAsNumber))
                {
                    return label;
                }

                return (labelAsNumber * -1).toString();
            }

        ]]>
    </mx:Script>

    <!-- Define custom colors for use as fills. -->
    <mx:SolidColor id="sc1" color="yellow" alpha=".8"/>

    <!-- Define custom Strokes for the columns. -->
    <mx:Stroke id="s1" color="yellow" weight="2"/>

    <mx:Panel title="ColumnChart and BarChart Controls Example" 
        height="100%" width="100%" layout="horizontal">
        <mx:LineChart id="column" 
            height="100%" 
            width="100%" 
            paddingLeft="5" 
            paddingRight="5" 
            showDataTips="true" 
            dataProvider="{timeValue}" >

            <mx:horizontalAxis>
                <mx:LinearAxis id="horizontalAxis" maximum="0" minimum="-10" parseFunction="{verticalAxisParseFunction}"/>
            </mx:horizontalAxis>

            <mx:verticalAxis>
                <mx:LinearAxis id="verticalAxis" maximum="100" minimum="0" />           
            </mx:verticalAxis>

            <mx:horizontalAxisRenderers>
                <mx:AxisRenderer
                    axis="{horizontalAxis}"
                    labelFunction="{horizontalAxisRenderedLabelFunction}" />
            </mx:horizontalAxisRenderers>

            <mx:verticalAxisRenderers>
                <mx:AxisRenderer
                    axis="{verticalAxis}"
                    placement="right" />
            </mx:verticalAxisRenderers>


            <mx:series>
                <mx:LineSeries 
                    xField="Time" 
                    yField="Value" 
                    displayName="TimeValue"
                    fill="{sc1}"
                    stroke="{s1}"
                />
            </mx:series>
        </mx:LineChart>

    </mx:Panel>
</mx:Application>