How to make a line graph using CorePlot framework and swift 3? - ios

Question

I can't understand how to make a line plot with CorePlot 2.2 with Swift 3 (Xcode 8, iOS 10).
Can someone explain how to do it?
Particularly, I don't understand how the last function numbers (line 97-103(last lines)) works:
import UIKit
import CorePlot
class dottedLine: UIViewController {
#IBOutlet var hostView: CPTGraphHostingView!
var plot: CPTScatterPlot!
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
initPlot()
}
let xValues: [NSNumber] = [1,2,3,4]
let yValues: [NSNumber] = [1,5,4,3]
func initPlot() {
configureHostView()
configureGraph()
configureChart()
configureAxes()
}
func configureHostView() {
hostView.allowPinchScaling = false
}
func configureGraph() {
// 1 - Create the graph
let graph = CPTXYGraph(frame: hostView.bounds)
graph.plotAreaFrame?.masksToBorder = false
hostView.hostedGraph = graph
// 2 - Configure the graph
//graph.apply(CPTTheme(named: CPTThemeName.plainWhiteTheme))
//graph.fill = CPTFill(color: CPTColor.clear())
graph.paddingBottom = 30.0
graph.paddingLeft = 30.0
graph.paddingTop = 0.0
graph.paddingRight = 0.0
// 3 - Set up styles
let titleStyle = CPTMutableTextStyle()
titleStyle.color = CPTColor.black()
titleStyle.fontName = "HelveticaNeue-Bold"
titleStyle.fontSize = 16.0
titleStyle.textAlignment = .center
graph.titleTextStyle = titleStyle
let title = "Just title"
graph.title = title
graph.titlePlotAreaFrameAnchor = .top
graph.titleDisplacement = CGPoint(x: 0.0, y: -16.0)
// 4 - Set up plot space
let xMin = 0.0
let xMax = 5.0
let yMin = 0.0
let yMax = 15.0
guard let plotSpace = graph.defaultPlotSpace as? CPTXYPlotSpace else { return }
plotSpace.xRange = CPTPlotRange(locationDecimal: CPTDecimalFromDouble(xMin), lengthDecimal: CPTDecimalFromDouble(xMax - xMin))
plotSpace.yRange = CPTPlotRange(locationDecimal: CPTDecimalFromDouble(yMin), lengthDecimal: CPTDecimalFromDouble(yMax - yMin))
}
func configureChart() {
// 1 - Set up the plot
plot = CPTScatterPlot()
// 2 - Set up style
let plotLineStile = CPTMutableLineStyle()
plotLineStile.lineWidth = 1
plotLineStile.lineColor = CPTColor.black()
plot.dataLineStyle = plotLineStile
// 3- Add plots to graph
guard let graph = hostView.hostedGraph else { return }
plot.dataSource = self
plot.delegate = self
graph.add(plot, to: graph.defaultPlotSpace)
}
func configureAxes() {
}
}
extension dottedLine: CPTScatterPlotDataSource, CPTScatterPlotDelegate {
func numberOfRecords(for plot: CPTPlot) -> UInt {
// number of points
return UInt(xValues.count)
}
func scatterPlot(_ plot: CPTScatterPlot, plotSymbolWasSelectedAtRecord idx: UInt, with event: UIEvent) {
}
/* func numbers(for plot: CPTPlot, field fieldEnum: UInt, recordIndexRange indexRange: NSRange) -> [Any]? {
print("xxxxxxx")
switch CPTScatterPlotField(rawValue: Int(fieldEnum))! {
case .X:
return xValues[index] as NSNumber
case .Y:
return yValues[indexRange] as NSNumber
}
} */
/* func symbols(for plot: CPTScatterPlot, recordIndexRange indexRange: NSRange) -> [CPTPlotSymbol]? {
return xValues
} */
func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any? {
switch CPTScatterPlotField(rawValue: Int(field))! {
case .X:
return 2 as NSNumber
case .Y:
return 3 as NSNumber
}
}
}

Answer 1

For a scatter plot, this method will be called once for the x-value and once for the y-value at each index.
Here is that method from the DatePlot example app:
func number(for plot: CPTPlot, field: UInt, record: UInt) -> Any?
{
switch CPTScatterPlotField(rawValue: Int(field))! {
case .X:
return (oneDay * Double(record)) as NSNumber
case .Y:
return self.plotData[Int(record)] as NSNumber
}
}