Charts: Filled Line Chart

[sunynator]

I'm trying to draw a filled line chart, you guys can see the picture for more clarity.

So, I saw the example and they are using IFillFormatter protocol to get y-axis position where the filled line of dataset end. But, it was a fixed position, not dynamic at all. How can I can this position depend on the each element of dataset. For instance, if index == 0 then we have a the end of filled position A, if index == 1 then we have a different end value of a filled position.
Or, any other suggestion to draw a chart like the picture above.

[liuxuan30]

take a look at drawLinearFill where it draw the fill rect. It calculates the fill rect within generateFilledPath and getFillLinePosition. ideally you should override those methods to get your rect between lines, you are good to go

[rob-k]

I managed to achieve this by following @liuxuan30 's suggestions by subclassing LineChartRenderer and adding a variable to the class implementing IFillFormatter, which let's me pass a second data set as indicator for the fill line and draw the path accordingly (only for linear, but I assume you could do the same thing for Bezier).

class AreaFillFormatter: IFillFormatter {

    var fillLineDataSet: LineChartDataSet?

    init(fillLineDataSet: LineChartDataSet) {
        self.fillLineDataSet = fillLineDataSet
    }

    public func getFillLinePosition(dataSet: ILineChartDataSet, dataProvider: LineChartDataProvider) -> CGFloat {
        return 0.0
    }

    public func getFillLineDataSet() -> LineChartDataSet {
        return fillLineDataSet ?? LineChartDataSet()
    }

}

class CustomLineChartRenderer: LineChartRenderer {

    override open func drawLinearFill(context: CGContext, dataSet: ILineChartDataSet, trans: Transformer, bounds: XBounds) {
        guard let dataProvider = dataProvider else { return }

        let areaFillFormatter = dataSet.fillFormatter as? AreaFillFormatter

        let filled = generateFilledPath(
            dataSet: dataSet,
            fillMin: dataSet.fillFormatter?.getFillLinePosition(dataSet: dataSet, dataProvider: dataProvider) ?? 0.0,
            fillLineDataSet: areaFillFormatter?.getFillLineDataSet(),
            bounds: bounds,
            matrix: trans.valueToPixelMatrix)

        if dataSet.fill != nil
        {
            drawFilledPath(context: context, path: filled, fill: dataSet.fill!, fillAlpha: dataSet.fillAlpha)
        }
        else
        {
            drawFilledPath(context: context, path: filled, fillColor: dataSet.fillColor, fillAlpha: dataSet.fillAlpha)
        }
    }

    fileprivate func generateFilledPath(dataSet: ILineChartDataSet, fillMin: CGFloat, fillLineDataSet: ILineChartDataSet?, bounds: XBounds, matrix: CGAffineTransform) -> CGPath
    {
        let phaseY = animator?.phaseY ?? 1.0
        let isDrawSteppedEnabled = dataSet.mode == .stepped
        let matrix = matrix

        var e: ChartDataEntry!
        var fillLineE: ChartDataEntry?

        let filled = CGMutablePath()

        e = dataSet.entryForIndex(bounds.min)
        fillLineE = fillLineDataSet?.entryForIndex(bounds.min)

        if e != nil
        {
            if let fillLineE = fillLineE
            {
                filled.move(to: CGPoint(x: CGFloat(e.x), y: CGFloat(fillLineE.y * phaseY)), transform: matrix)
            }
            else
            {
                filled.move(to: CGPoint(x: CGFloat(e.x), y: fillMin), transform: matrix)
            }

            filled.addLine(to: CGPoint(x: CGFloat(e.x), y: CGFloat(e.y * phaseY)), transform: matrix)
        }

        // Create the path for the data set entries
        for x in stride(from: (bounds.min + 1), through: bounds.range + bounds.min, by: 1)
        {
            guard let e = dataSet.entryForIndex(x) else { continue }

            if isDrawSteppedEnabled
            {
                guard let ePrev = dataSet.entryForIndex(x-1) else { continue }
                filled.addLine(to: CGPoint(x: CGFloat(e.x), y: CGFloat(ePrev.y * phaseY)), transform: matrix)
            }

            filled.addLine(to: CGPoint(x: CGFloat(e.x), y: CGFloat(e.y * phaseY)), transform: matrix)
        }

        // Draw a path to the start of the fill line
        e = dataSet.entryForIndex(bounds.range + bounds.min)
        fillLineE = fillLineDataSet?.entryForIndex(bounds.range + bounds.min)
        if e != nil
        {
            if let fillLineE = fillLineE
            {
                filled.addLine(to: CGPoint(x: CGFloat(e.x), y: CGFloat(fillLineE.y * phaseY)), transform: matrix)
            }
            else
            {
                filled.addLine(to: CGPoint(x: CGFloat(e.x), y: fillMin), transform: matrix)
            }
        }

        // Draw the path for the fill line (backwards)
        if let fillLineDataSet = fillLineDataSet {
            for x in stride(from: (bounds.min + 1), through: bounds.range + bounds.min, by: 1).reversed()
            {
                guard let e = fillLineDataSet.entryForIndex(x) else { continue }

                if isDrawSteppedEnabled
                {
                    guard let ePrev = fillLineDataSet.entryForIndex(x-1) else { continue }
                    filled.addLine(to: CGPoint(x: CGFloat(e.x), y: CGFloat(ePrev.y * phaseY)), transform: matrix)
                }

                filled.addLine(to: CGPoint(x: CGFloat(e.x), y: CGFloat(e.y * phaseY)), transform: matrix)
            }
        }

        filled.closeSubpath()

        return filled
    }
}

[liuxuan30]

perfect example to mastering the project :)

[jjy4880]

how to resolve/ use this solution?

[bhargavsejpalindianic]

@rob-k can you please provide usage example for this

[rob-k]

Sure, I use the code as follows:

let maxDataSet = LineChartDataSet()
let minDataSet = LineChartDataSet()

// ... fill the data sets

// Set the data
self.lineChart.data = LineChartData(dataSets: [maxDataSet, minDataSet])

// Set the custom line chart renderer
self.lineChart.renderer = CustomLineChartRenderer(dataProvider: self.lineChart, animator: self.lineChart.chartAnimator, viewPortHandler: self.lineChart.viewPortHandler)

maxDataSet.drawFilledEnabled = true
maxDataSet.fillFormatter = AreaFillFormatter(fillLineDataSet: minDataSet)

[bhargavsejpalindianic]

i installed this manually and followed each step as per example still looks like its not working @rob-k

[bhargavsejpalindianic]

@rob-k i tried to debug using break points any of function from CustomLineChartRenderer not being called

[rob-k]

I updated my comment to include setting the LineChartRenderer.

[bhargavsejpalindianic]

still no luck man @rob-k

[rob-k]

If you want the color between ucbDataSet and lcbDataSet you need to pass the second data set to the formatter of the first one. You are passing the dataset to the formatter of itself. Try to do the following:

ucbDataSet.fillFormatter = AreaFillFormatter(fillLineDataSet: lcbDataSet)

(or the other way around)

[bhargavsejpalindianic]

already tried what i am trying to explain is
i tried to debug using break points any of function from CustomLineChartRenderer class not being called

[rob-k]

I see that you are using Bezier mode in your code:

lineChartDataSet.mode = .horizontalBezier
ucbDataSet.mode = .horizontalBezier
lcbDataSet.mode = .horizontalBezier

The code I provided only works for linear mode. You will have to change the mode to .linear or override drawHorizontalBezier and adjust the code accordingly.

[bhargavsejpalindianic]

@rob-k got it just worked thanks very much man for finding it out

[michal-th]

Would it be possible to implement this using CombinedChart ?

[Chakib-Temal]

Would it be possible to implement this using CombinedChart ?

did you find the solution ? the CombinedChart use the CombinedChartRender , not the LinearChartRender , so the call back is not called drawLinearFill , it use the default Render

the method drawLinearFill doesn't exist , it's take many of new renders when you search in the library

[Chakib-Temal]

Would it be possible to implement this using CombinedChart ?

solution combinedChart : https://github.com/PhilJay/MPAndroidChart/issues/338