Is there a way to use Line Chart with custom xAxis?

[katisari]

I'm trying to create a Line Chart with custom xAxis labels.
I want to put different categories in the axis for such as ["january", "Feb", "March"]. Is there any way to do that for line charts?

[MaxDesiatov]

Strong +1 for this, my use case is displaying time series data, where x values are of NSTimeInterval type, but should be formatted as dates on the x axis.

[katisari]

Does it appear as strings later on the Dax is? I want to later test it for dog properties such as life span etc on the x axis

…

On Wed, Jul 25, 2018 at 8:30 AM Max Desiatov ***@***.***> wrote: Strong +1 for this, my use case is displaying time series data, where x values are of NSTimeInterval type, but should be formatted as dates on the x axis. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3579 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AlXR6lcVdZn0mBM0Sa1eLaCzyJzqVJ8Vks5uKI8cgaJpZM4VgQ2Q> .

[thierryH91200]

look at #3069

[MaxDesiatov]

It only appears as a formatted Double, because ChartDataEntry type is not generic and supports only Double for both x and y, while it doesn't provide any customisation points for formatting at all.

[katisari]

Does this mean that I won't be able to insert strings on the x-axis? Would it be only possible for barographs? I want to use a line graph but with categories in strings on the x-axis.

[MaxDesiatov]

After a quick investigation, looks like IAxisValueFormatter could solve this:

import Charts
import UIKit

final class DateValueFormatter: IAxisValueFormatter {
  func stringForValue(_ value: Double, axis: AxisBase?) -> String {
    return formatter.string(from: Date(timeIntervalSinceReferenceDate: value))
  }

  let formatter: DateFormatter

  init(formatter: DateFormatter) {
    self.formatter = formatter
  }
}

let dataSetSize: CGFloat = 14

final class ViewController: UIViewController {
  @IBOutlet weak var chartView: LineChartView!

  func refresh() {
    // Do any additional setup after loading the view.
    let ys1 = Array(1..<10).map { sin(Double($0) / 2.0 / 3.141 * 1.5) }
    let ys2 = Array(1..<10).map { cos(Double($0) / 2.0 / 3.141) }

    let yse1 = ys1.enumerated().map { ChartDataEntry(x: Double($0), y: $1) }
    let yse2 = ys2.enumerated().map { ChartDataEntry(x: Double($0), y: $1) }

    let data = LineChartData()
    let ds1 = LineChartDataSet(values: yse1, label: "Hello")
    ds1.valueFont = .systemFont(ofSize: dataSetSize)
    ds1.colors = [.red]
    data.addDataSet(ds1)

    let ds2 = LineChartDataSet(values: yse2, label: "World")
    ds2.valueFont = .systemFont(ofSize: dataSetSize)
    ds2.colors = [.blue]
    data.addDataSet(ds2)

    let f = DateFormatter()
    f.dateStyle = .short
    chartView.xAxis.valueFormatter = DateValueFormatter(formatter: f)
    chartView.data = data

    chartView.gridBackgroundColor = .lightGray
    chartView.backgroundColor = .white

    chartView.chartDescription?.text = "Linechart Demo"
  }

  override func viewDidLoad() {
    super.viewDidLoad()

    refresh()
  }
}

[thierryH91200]

it's false

final class DateValueFormatter: IAxisValueFormatter {
  func stringForValue(_ value: Double, axis: AxisBase?) -> String {
    return formatter.string(from: Date(timeIntervalSinceReferenceDate: value))
  }

  let formatter: DateFormatter

  init(formatter: DateFormatter) {
    self.formatter = formatter
  }
}

IAxisValueFormatter is obsolete

[MaxDesiatov]

@thierryH91200 would you kindly provide any documentation or references that confirm that this protocol is obsolete? In the latest Charts 3.1.1 it's not marked as either obsolete or deprecated and the example code I provided works perfectly well and is able to change X axis labels without a problem.

Please have a look at the attached screenshot, which is made from the example code from my comment above.

[thierryH91200]

it's a mistake
mea culpa
I work with 4.0.0

I was too fast

@objc(ChartAxisBase)
open class AxisBase: ComponentBase
{
    public override init()
    {
        super.init()
    }
    
    /// Custom formatter that is used instead of the auto-formatter if set
    private lazy var _axisValueFormatter: AxisValueFormatter = DefaultAxisValueFormatter(decimals: decimals)
    
    @objc open var labelFont = NSUIFont.systemFont(ofSize: 10.0)
    @objc open var labelTextColor = NSUIColor.black
  

[katisari]

This is what I'm getting. But I want the x-axis labels to be a string and not in the format of a date. Specifically, I want to put ["height", age"] in the x-axis. Is there a way to do this?

[MaxDesiatov]

@katisari change func stringForValue(_ value: Double, axis: AxisBase?) -> String in your IAxisValueFormatter implementation to convert X values to strings as needed. I don't know what are your sample X values to provide more info.

[katisari]

Okay that works! But do I have to use date formatter in the class that's inheriting from the IAxisValueFormatter? Am I allowed to change formatter variable to type String? It throws me an error when I try to do that.

[MaxDesiatov]

@katisari you don't have to use a date formatter, you can produce whatever string is needed as long as your formatter conforms to IAxisValueFormatter protocol, which is super-simple: https://github.com/danielgindi/Charts/blob/v3.1.1/Source/Charts/Formatters/IAxisValueFormatter.swift

[liuxuan30]

Seems it's answered by great people, closing.