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

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)
}

Answer 2

You got something wrong here. Right now you are creating a new DataSet for every year.
What you need to do is create as many DataSets as you want bars per group where one DataSet represents one bar in each group. (e.g. DataSet 1 represents every first bar of a group, DataSet 2 every second bar of a group, ...)
As an example, imagine a chart like this with 4 groups of 3 bars per group. Each group represents one year.
||| ||| ||| |||
The setup shown above requires 3 DataSets (one for each group)
Entries in the same group have the same x-index (e.g. in the first group all have x-index 0)
It consists of a total of 12 entries
Each DataSet contains 4 entries with Entry x-indices ranging from 0 to 3
Here you can find an example of the scenario described above and check out the documentation.

Answer 3

if you have noticed in above code in function chart. There is let
groupSpace = 0.3
let barSpace = 0.05
let barWidth = 0.3
// (0.3 + 0.05) * 2 + 0.3 = 1.00 -> interval per "group"
which will make equation
(groupSpace * barSpace) * n + groupSpace = 1
you need to play around this equation for n number of bars

Answer 4

I've tried Rajan Twanabashu solution, but it was almost the good one. Maybe it has changed since, I don't know.
Here's what I've done, after I found the groupWidth function in the BarDataChart file from Charts.
groupWidth function declaration
let groupSpace = 1 - n * (barWidth + barSpace)
Hope it could help

Answer 5

After diving in this equation "(0.3 + 0.05) * 2 + 0.3 = 1.00" to work on variant amount of grouping I got:
let n = Double(data.dataSets.count)
let groupSpace = 0.0031 * n
let barSpace = 0.002 * n
let barWidth = (1 - (n * barSpace) - groupSpace) / n
What is varying is barWidth.