Bar Chart jumps up when there's more than 2 columns - ios

Question

I am working on a chart with data set change when the button is pressed. But it looks like when I have more than 2 bars, the chart origin point shifts.
Two columns is fine:
Creating data set:
private func buildMoodDummyBarData(period: Period) -> [BarChartDataEntry] {
if period == .week {
let entry1 = BarChartDataEntry(x: 0, y: 720)
let entry2 = BarChartDataEntry(x: 1, y: 440)
let entry3 = BarChartDataEntry(x: 2, y: 0)
let entry4 = BarChartDataEntry(x: 3, y: 30)
let entry5 = BarChartDataEntry(x: 4, y: 30)
return [entry1, entry2, entry3, entry4, entry5]
} else if period == .month {
let entry1 = BarChartDataEntry(x: 0, y: 100)
let entry2 = BarChartDataEntry(x: 1, y: 300)
let entry3 = BarChartDataEntry(x: 2, y: 50)
let entry4 = BarChartDataEntry(x: 3, y: 30)
let entry5 = BarChartDataEntry(x: 4, y: 30)
return [entry1, entry2, entry3, entry4, entry5]
} else {
return []
}
}
Finishing building data set and changing bar colors:
func buildMoodBarData(period: Period) -> BarChartData? {
let entries = buildMoodDummyBarData(period: period)
let set = BarChartDataSet(values: entries, label: nil)
set.highlightEnabled = false
let tempData = BarChartData(dataSet: set) // Just to find max
let max = tempData.yMax
let onePercent = max / 100
var colors = [UIColor]()
for item in entries {
let percentValue = item.y / onePercent
colors.append(setColor(value: percentValue))
}
set.colors = colors
let data = BarChartData(dataSet: set)
data.setDrawValues(true)
data.barWidth = 0.72
return data
}
// barChartView is storyboard outlet
private func makeMoodBarChart() {
barChartView.backgroundColor = UIColor.red
barChartView.chartDescription = nil
barChartView.leftAxis.enabled = false
barChartView.rightAxis.enabled = false
barChartView.legend.enabled = false
barChartView.xAxis.enabled = false
}
private func updateMoodBarChart(with data: BarChartData) {
barChartView.data = data
barChartView.fitBars = false
barChartView.fitScreen()
}

Answer 1

The problem is related to data set. When I replaced it to following data, problem disappeared. I think issue occurs because Y scale values was changing too much.
private func buildMoodDummyBarData(period: Period) -> [BarChartDataEntry] {
if period == .week {
let entry1 = BarChartDataEntry(x: 0, y: 10)
let entry2 = BarChartDataEntry(x: 1, y: 50)
let entry3 = BarChartDataEntry(x: 2, y: 100)
let entry4 = BarChartDataEntry(x: 3, y: 20)
let entry5 = BarChartDataEntry(x: 4, y: 30)
return [entry1, entry2, entry3, entry4, entry5]
} else if period == .month {
let entry1 = BarChartDataEntry(x: 0, y: 100)
let entry2 = BarChartDataEntry(x: 1, y: 30)
let entry3 = BarChartDataEntry(x: 2, y: 30)
let entry4 = BarChartDataEntry(x: 3, y: 20)
let entry5 = BarChartDataEntry(x: 4, y: 30)
return [entry1, entry2, entry3, entry4, entry5]
} else {
return []
}
}
This doesn't mean min and max value has to be exactly the same in both data sets (20 to 100), however if difference is too big (30 to 320 in first data set and 30 to 720 in second), chart baseline changes.
This is not ideal solution.

Answer 2

While updating Barchart with new dataset make chartdata as nil
if let bardata = buildMoodBarData(period: state) {
barChatView.data = nil
updateMoodBarChart(with: bardata)
}