swift - How to make a grouped BarChart with ios-charts?

Question

I am using ios-charts library.

I would like to group my inverter values so that each year is one group. Unfortunately, the number of monthly values per year may vary.

My data json looks like this:

{"monthlyData":[{"ERTRAG":"30.2989999055862","MONAT":"2","JAHR":"2016"},{"ERTRAG":"154.897000223398","MONAT":"1","JAHR":"2016"},{"ERTRAG":"141.996000155807","MONAT":"12","JAHR":"2015"},{"ERTRAG":"135.449000149965","MONAT":"11","JAHR":"2015"},{"ERTRAG":"319.437000751495","MONAT":"10","JAHR":"2015"},{"ERTRAG":"483.369997739792","MONAT":"9","JAHR":"2015"},{"ERTRAG":"698.112997770309","MONAT":"8","JAHR":"2015"},{"ERTRAG":"771.764000892639","MONAT":"7","JAHR":"2015"},{"ERTRAG":"736.611003398895","MONAT":"6","JAHR":"2015"},{"ERTRAG":"737.237999916077","MONAT":"5","JAHR":"2015"},{"ERTRAG":"720.181995391846","MONAT":"4","JAHR":"2015"},{"ERTRAG":"484.979001283646","MONAT":"3","JAHR":"2015"},{"ERTRAG":"249.974001646042","MONAT":"2","JAHR":"2015"},{"ERTRAG":"92.8830004036427","MONAT":"1","JAHR":"2015"},{"ERTRAG":"52.7970000207424","MONAT":"12","JAHR":"2014"},{"ERTRAG":"181.025999426842","MONAT":"11","JAHR":"2014"},{"ERTRAG":"332.789002537727","MONAT":"10","JAHR":"2014"},{"ERTRAG":"482.244999885559","MONAT":"9","JAHR":"2014"},{"ERTRAG":"602.811999320984","MONAT":"8","JAHR":"2014"},{"ERTRAG":"699.872003316879","MONAT":"7","JAHR":"2014"},{"ERTRAG":"828.212007522583","MONAT":"6","JAHR":"2014"},{"ERTRAG":"679.010004997253","MONAT":"5","JAHR":"2014"},{"ERTRAG":"635.115998744965","MONAT":"4","JAHR":"2014"},{"ERTRAG":"559.617002010345","MONAT":"3","JAHR":"2014"},{"ERTRAG":"265.135001063347","MONAT":"2","JAHR":"2014"},{"ERTRAG":"165.272998273373","MONAT":"1","JAHR":"2014"},{"ERTRAG":"134.578999936581","MONAT":"12","JAHR":"2013"},{"ERTRAG":"153.774000287056","MONAT":"11","JAHR":"2013"},{"ERTRAG":"321.733997344971","MONAT":"10","JAHR":"2013"},{"ERTRAG":"482.768000483513","MONAT":"9","JAHR":"2013"},{"ERTRAG":"692.864000797272","MONAT":"8","JAHR":"2013"},{"ERTRAG":"846.429007053375","MONAT":"7","JAHR":"2013"},{"ERTRAG":"709.758005619049","MONAT":"6","JAHR":"2013"},{"ERTRAG":"532.493996858597","MONAT":"5","JAHR":"2013"},{"ERTRAG":"462.539998054504","MONAT":"4","JAHR":"2013"},{"ERTRAG":"419.105004012585","MONAT":"3","JAHR":"2013"},{"ERTRAG":"143.189998820424","MONAT":"2","JAHR":"2013"},{"ERTRAG":"78.720000628382","MONAT":"1","JAHR":"2013"},{"ERTRAG":"90.1430006623268","MONAT":"12","JAHR":"2012"},{"ERTRAG":"155.483000457287","MONAT":"11","JAHR":"2012"},{"ERTRAG":"348.231998205185","MONAT":"10","JAHR":"2012"},{"ERTRAG":"598.037001848221","MONAT":"9","JAHR":"2012"},{"ERTRAG":"729.740003108978","MONAT":"8","JAHR":"2012"},{"ERTRAG":"676.923998832703","MONAT":"7","JAHR":"2012"},{"ERTRAG":"694.879002094269","MONAT":"6","JAHR":"2012"},{"ERTRAG":"811.281997680664","MONAT":"5","JAHR":"2012"},{"ERTRAG":"489.765002369881","MONAT":"4","JAHR":"2012"},{"ERTRAG":"538.866001605988","MONAT":"3","JAHR":"2012"},{"ERTRAG":"277.856996208429","MONAT":"2","JAHR":"2012"},{"ERTRAG":"155.854999214411","MONAT":"1","JAHR":"2012"},{"ERTRAG":"148.157999750227","MONAT":"12","JAHR":"2011"},{"ERTRAG":"230.409998774529","MONAT":"11","JAHR":"2011"}]}

I tried the following:

var months = Array<String>()
var years = Array<String>()
var dataEntries: [BarChartDataEntry] = []
var dataSets: [BarChartDataSet] = []
var overallSum = 0.0
var year = 2010 //monthlyValues[0].year
var count = 0
var chartDataSet: BarChartDataSet?

for i in 0..<monthlyValues.count {
  // if year is different, create new barchartdataset
  if monthlyValues[i].year != year {
    years.append("(monthlyValues[i].year)")
    chartDataSet = BarChartDataSet(yVals: dataEntries, label: "(year)")
    chartDataSet!.colors = [UIColor.whiteColor()]
    dataSets.append(chartDataSet!)
    year = monthlyValues[i].year
    dataEntries = []
    //months = []
    count = 0
  }
  months.append("(monthlyValues[i].month)")
  overallSum += monthlyValues[i].amount

  let dataEntry = BarChartDataEntry(value: monthlyValues[i].amount, xIndex: count)
  count++
  dataEntries.append(dataEntry)
}
let chartData = BarChartData(xVals: months, dataSets: dataSets)
self.barChartView.data = chartData

This results in five series with the right year labels in the legend but there is no group separator in the chart and also the number of bars per year is either 4 or 5 (expected = 12).

Thanks for any hint on this!

Answer 1

let months = ["Jan", "Feb", "Mar", "Apr", "May"]
    let unitsSold = [20.0, 4.0, 6.0, 3.0, 12.0]
    let unitsBought = [10.0, 14.0, 60.0, 13.0, 2.0]

     override func viewDidLoad() {
            super.viewDidLoad()
            // Do any additional setup after loading the view, typically from a nib.
            barChartView.delegate = self
            barChartView.noDataText = "You need to provide data for the chart."
            barChartView.chartDescription?.text = "sales vs bought "


            //legend
            let legend = barChartView.legend
            legend.enabled = true
            legend.horizontalAlignment = .right
            legend.verticalAlignment = .top
            legend.orientation = .vertical
            legend.drawInside = true
            legend.yOffset = 10.0;
            legend.xOffset = 10.0;
            legend.yEntrySpace = 0.0;


            let xaxis = barChartView.xAxis
            xaxis.valueFormatter = axisFormatDelegate
            xaxis.drawGridLinesEnabled = true
            xaxis.labelPosition = .bottom
            xaxis.centerAxisLabelsEnabled = true
            xaxis.valueFormatter = IndexAxisValueFormatter(values:self.months)
            xaxis.granularity = 1


            let leftAxisFormatter = NumberFormatter()
            leftAxisFormatter.maximumFractionDigits = 1

            let yaxis = barChartView.leftAxis
            yaxis.spaceTop = 0.35
            yaxis.axisMinimum = 0
            yaxis.drawGridLinesEnabled = false

            barChartView.rightAxis.enabled = false
           //axisFormatDelegate = self

            setChart()
        }

 func setChart() {
        barChartView.noDataText = "You need to provide data for the chart."
        var dataEntries: [BarChartDataEntry] = []
        var dataEntries1: [BarChartDataEntry] = []

        for i in 0..<self.months.count {

            let dataEntry = BarChartDataEntry(x: Double(i) , y: self.unitsSold[i])
            dataEntries.append(dataEntry)

            let dataEntry1 = BarChartDataEntry(x: Double(i) , y: self.self.unitsBought[i])
            dataEntries1.append(dataEntry1)

            //stack barchart
            //let dataEntry = BarChartDataEntry(x: Double(i), yValues:  [self.unitsSold[i],self.unitsBought[i]], label: "groupChart")



        }

        let chartDataSet = BarChartDataSet(values: dataEntries, label: "Unit sold")
        let chartDataSet1 = BarChartDataSet(values: dataEntries1, label: "Unit Bought")

        let dataSets: [BarChartDataSet] = [chartDataSet,chartDataSet1]
        chartDataSet.colors = [UIColor(red: 230/255, green: 126/255, blue: 34/255, alpha: 1)]
        //chartDataSet.colors = ChartColorTemplates.colorful()
        //let chartData = BarChartData(dataSet: chartDataSet)

        let chartData = BarChartData(dataSets: dataSets)


        let groupSpace = 0.3
        let barSpace = 0.05
        let barWidth = 0.3
        // (0.3 + 0.05) * 2 + 0.3 = 1.00 -> interval per "group" 

        let groupCount = self.months.count
        let startYear = 0


        chartData.barWidth = barWidth;
        barChartView.xAxis.axisMinimum = Double(startYear)
        let gg = chartData.groupWidth(groupSpace: groupSpace, barSpace: barSpace)
        print("Groupspace: (gg)")
        barChartView.xAxis.axisMaximum = Double(startYear) + gg * Double(groupCount)

        chartData.groupBars(fromX: Double(startYear), groupSpace: groupSpace, barSpace: barSpace)
        //chartData.groupWidth(groupSpace: groupSpace, barSpace: barSpace)
        barChartView.notifyDataSetChanged()

        barChartView.data = chartData






        //background color
        barChartView.backgroundColor = UIColor(red: 189/255, green: 195/255, blue: 199/255, alpha: 1)

        //chart animation
        barChartView.animate(xAxisDuration: 1.5, yAxisDuration: 1.5, easingOption: .linear)


    }