Slider going back to its original position (onEditingChanged)

Question

I have a slider that controls the day of the year. In the chart the calculations are time consuming, so if you move the slider a lot it can take an age to finish the update, as it's regenerating each intermediary view.

So, I introduced an onEditingChanged to manage this.

HStack {
      Slider(value: $daySlider, in: 0...364, onEditingChanged: { (isBegin) in
          if isBegin {
                sliderUpdate = false  // Begins sliding
          } else {
                sliderUpdate = true   // Finishes sliding
          }
     })
 }

There are two related phenomena going on here:

i) When you release the slider it goes back to its original value.

ii) Due to the way I have written the interim code the chart evaporates whilst the slider is being moved, so you just see.

The code for the chart is, where sliderUpdate is a State variable:

 func AnimatedChart()->some View{
        if sliderUpdate == true {
            Chart{
                let filteredArray = solarElevation.filter { $0.day == Int(daySlider) }
                ForEach(filteredArray) {item in
                    LineMark(
                        x: .value("Hour", ((Calendar.current.dateComponents(components, from: item.date).hour!))+1),
                        y: .value("Elevation", item.elevation),
                        series: .value("Hour", "Elevation")
                    )
                    .interpolationMethod(.catmullRom)
                    .lineStyle(StrokeStyle(lineWidth: 2))
                    .foregroundStyle(.blue)
                }
                let filteredArrayHour = solarElevation.filter { $0.day == Int(daySlider) && $0.hour == Int(hourSlider) }
                ForEach(filteredArrayHour) {itemRule in

                    RuleMark(x: .value("Hour", itemRule.hour + 1))
                        .foregroundStyle(Color.orange)
                        .lineStyle(StrokeStyle(lineWidth: 1))
                    PointMark(
                        x: .value("Hour", itemRule.hour + 1),
                        y: .value("Elevation", itemRule.elevation)
                    )
                    .foregroundStyle(.orange)
                }
            }
            .frame(height: 300)
            .chartXAxisLabel(position: .bottom, alignment: .center) { Text("Hours") }
           // .chartXScale(domain: 0...24)
            .chartXAxis{
                AxisMarks(values: [0, 6, 12, 18, 24])
            }
            .chartYScale(domain: -90...90)
            .onAppear {
                daySlider = Double(Celestial().calculateDayOfYear(Date()))
                animateGraph()
            }
        }
        else {
        }
    }

What do I need to do?