This example shows persistence of old traces giving a ‘ghosted’ or digital phosphor effect.

The example updates 10 series each with 1,000 points in realtime while setting the opacity of series on each timer tick. As new series are drawn older series are made increasingly transparent until they become invisible.

// RealTimeGhostTracesChartView.m

//******************************************************************************
// SCICHART® Copyright SciChart Ltd. 2011-2019. All rights reserved.
//
// Web: http://www.scichart.com
// Support: support@scichart.com
// Sales:   sales@scichart.com
//
// RealTimeGhostTracesChartView.m is part of the SCICHART® Examples. Permission is hereby granted
// to modify, create derivative works, distribute and publish any part of this source
// code whether for commercial, private or personal use.
//
// The SCICHART® examples are distributed in the hope that they will be useful, but
// without any warranty. It is provided "AS IS" without warranty of any kind, either
// expressed or implied.
//******************************************************************************

#import "RealTimeGhostTracesChartView.h"
#import "SCDRealTimeGhostTracesToolbarItem.h"
#import "SCDDataManager.h"
#import "SCDRandomUtil.h"

@interface RealTimeGhostTracesChartView ()
@property (nonatomic, strong) SCDRealTimeGhostTracesToolbarItem *actionItem;
@end

@implementation RealTimeGhostTracesChartView {
    NSTimer *_timer;
    double _lastAmplitude;
    double _phase;
}

- (Class)associatedType { return SCIChartSurface.class; }

- (BOOL)showDefaultModifiersInToolbar { return NO; }

#if TARGET_OS_OSX
- (NSArray<id<ISCDToolbarItem>> *)provideExampleSpecificToolbarItems {
    return @[self.actionItem];
}
#elif TARGET_OS_IOS
- (SCIView *)providePanel {
    return [self.actionItem createView];
}
#endif

- (SCDRealTimeGhostTracesToolbarItem *)actionItem {
    if (!_actionItem) {
        __weak typeof(self) wSelf = self;
        _actionItem = [[SCDRealTimeGhostTracesToolbarItem alloc] initWithAction:^(double doubleValue) {
            if (doubleValue > 0) {
                if (self->_timer != nil) {
                    [self->_timer invalidate];
                }
                [wSelf p_SCD_startTimerWithValue:doubleValue];
            }
        }];
    }
    return _actionItem;
}

- (void)initExample {
    _lastAmplitude = 1.0;
    
    id<ISCIAxis> xAxis = [SCINumericAxis new];
    xAxis.autoRange = SCIAutoRange_Always;
    
    id<ISCIAxis> yAxis = [SCINumericAxis new];
    yAxis.autoRange = SCIAutoRange_Never;
    yAxis.visibleRange = [[SCIDoubleRange alloc] initWithMin:-2.0 max:2.0];
    
    [self.surface.xAxes add:xAxis];
    [self.surface.yAxes add:yAxis];
    
    uint limeGreen = 0xFF32CD32;
    
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:1.0];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.9];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.8];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.7];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.62];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.55];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.45];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.35];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.25];
    [self p_SCD_addLineRenderableSeries:limeGreen opacity:0.15];
    
    [self p_SCD_startTimerWithValue:_actionItem.sliderValue];
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    
    [_timer invalidate];
    _timer = nil;
}

- (void)p_SCD_startTimerWithValue:(double)value {
    _timer = [NSTimer scheduledTimerWithTimeInterval:value / 1000.0 target:self selector:@selector(p_SCD_updateData:) userInfo:nil repeats:YES];
}

- (void)p_SCD_updateData:(NSTimer *)timer {
    [SCIUpdateSuspender usingWithSuspendable:self.surface withBlock:^{
        SCIXyDataSeries *dataSeries = [[SCIXyDataSeries alloc] initWithXType:SCIDataType_Double yType:SCIDataType_Double];

        double randomAmplitude = self->_lastAmplitude + ([SCDRandomUtil nextDouble] - 0.5);
        if (randomAmplitude < -2.0) {
            randomAmplitude = -2.0;
        } else if (randomAmplitude > 2.0) {
            randomAmplitude = 2.0;
        }
        
        SCDDoubleSeries *noisySinewave = [SCDDataManager getNoisySinewaveWithAmplitude:randomAmplitude Phase:self->_phase PointCount:1000 NoiseAmplitude:0.25];
        self->_lastAmplitude = randomAmplitude;
    
        [dataSeries appendValuesX:noisySinewave.xValues y:noisySinewave.yValues];
        
        [self p_SCD_reassignRenderSeriesWithDataSeries:dataSeries];
    }];
}

- (void)p_SCD_reassignRenderSeriesWithDataSeries:(SCIXyDataSeries *)dataSeries {
    SCIRenderableSeriesCollection *rSeries = self.surface.renderableSeries;
    
    // shift old dataSeries
    [rSeries itemAt:9].dataSeries = [rSeries itemAt:8].dataSeries;
    [rSeries itemAt:8].dataSeries = [rSeries itemAt:7].dataSeries;
    [rSeries itemAt:7].dataSeries = [rSeries itemAt:6].dataSeries;
    [rSeries itemAt:6].dataSeries = [rSeries itemAt:5].dataSeries;
    [rSeries itemAt:5].dataSeries = [rSeries itemAt:4].dataSeries;
    [rSeries itemAt:4].dataSeries = [rSeries itemAt:3].dataSeries;
    [rSeries itemAt:3].dataSeries = [rSeries itemAt:2].dataSeries;
    [rSeries itemAt:2].dataSeries = [rSeries itemAt:1].dataSeries;
    [rSeries itemAt:1].dataSeries = [rSeries itemAt:0].dataSeries;
    
    // use new dataSeries to draw first renderableSeries
    [rSeries itemAt:0].dataSeries = dataSeries;
}

- (void)p_SCD_addLineRenderableSeries:(uint)color opacity:(float)opacity {
    SCIFastLineRenderableSeries *lineRenerableSeries = [SCIFastLineRenderableSeries new];
    lineRenerableSeries.opacity = opacity;
    lineRenerableSeries.strokeStyle = [[SCISolidPenStyle alloc] initWithColorCode:color thickness:1];
    
    [self.surface.renderableSeries add:lineRenerableSeries];
}

@end

// RealtimeGhostTracesLayout.xib

// RealtimeGhostTracesLayout.m

// RealTimeGhostedTracesChartView.swift

//******************************************************************************
// SCICHART® Copyright SciChart Ltd. 2011-2019. All rights reserved.
//
// Web: http://www.scichart.com
// Support: support@scichart.com
// Sales:   sales@scichart.com
//
// RealTimeGhostTracesChartView.swift is part of the SCICHART® Examples. Permission is hereby granted
// to modify, create derivative works, distribute and publish any part of this source
// code whether for commercial, private or personal use.
//
// The SCICHART® examples are distributed in the hope that they will be useful, but
// without any warranty. It is provided "AS IS" without warranty of any kind, either
// expressed or implied.
//******************************************************************************

class RealTimeGhostTracesChartView: SCDSingleChartWithTopPanelViewController<SCIChartSurface> {
    
    private lazy var actionItem: SCDRealTimeGhostTracesToolbarItem = {
        let item = SCDRealTimeGhostTracesToolbarItem { [weak self] doubleValue in
            guard let self = self else { return }
            
            if (doubleValue > 0) {
                self._timer?.invalidate()
                self.startTimer(with: doubleValue)
            }
        }
        return item
    }()
    
    private var _timer: Timer?
    private var _lastAmplitude = 1.0
    private var _phase = 0.0
    
    override var associatedType: AnyClass { return SCIChartSurface.self }
    
    override var showDefaultModifiersInToolbar: Bool { return false }

#if os(OSX)
    override func provideExampleSpecificToolbarItems() -> [ISCDToolbarItem] {
        return [actionItem]
    }
#elseif os(iOS)
    override func providePanel() -> SCIView {
        return actionItem.createView()
    }
#endif
    
    override func initExample() {
        let xAxis = SCINumericAxis()
        xAxis.autoRange = .always
        
        let yAxis = SCINumericAxis()
        yAxis.autoRange = .never
        yAxis.visibleRange = SCIDoubleRange.init(min: -2, max: 2)
        
        surface.xAxes.add(xAxis)
        surface.yAxes.add(yAxis)
        
        let limeGreen: uint = 0xFF32CD32
        
        addLineRenderableSeries(limeGreen, opacity: 1.0)
        addLineRenderableSeries(limeGreen, opacity: 0.9)
        addLineRenderableSeries(limeGreen, opacity: 0.8)
        addLineRenderableSeries(limeGreen, opacity: 0.7)
        addLineRenderableSeries(limeGreen, opacity: 0.62)
        addLineRenderableSeries(limeGreen, opacity: 0.55)
        addLineRenderableSeries(limeGreen, opacity: 0.45)
        addLineRenderableSeries(limeGreen, opacity: 0.35)
        addLineRenderableSeries(limeGreen, opacity: 0.25)
        addLineRenderableSeries(limeGreen, opacity: 0.15)

        startTimer(with: actionItem.sliderValue)
    }
    
    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        
        _timer?.invalidate()
        _timer = nil
    }
    
    private func startTimer(with sliderValue: Double) {
        _timer = Timer.scheduledTimer(timeInterval: sliderValue / 1000, target: self, selector: #selector(updateData), userInfo: nil, repeats: true)
    }
    
    @objc private func updateData(_ timer: Timer) {
        SCIUpdateSuspender.usingWith(surface) {
            let dataSeries = SCIXyDataSeries.init(xType: .double, yType: .double)

            var randomAmplitude:Double = self._lastAmplitude + (SCDRandomUtil.nextDouble() - 0.5)
            if (randomAmplitude < -2.0) {
                randomAmplitude = -2.0
            } else if (randomAmplitude > 2.0) {
                randomAmplitude = 2.0;
            }
            
            let noisySinewave = SCDDataManager.getNoisySinewave(withAmplitude: randomAmplitude, phase: self._phase, pointCount: 1000, noiseAmplitude: 0.25)
            self._lastAmplitude = randomAmplitude;
            
            dataSeries.append(x: noisySinewave.xValues, y: noisySinewave.yValues)
            self.reassignRenderSeriesWith(dataSeries: dataSeries)
        }
    }
    
    private func reassignRenderSeriesWith(dataSeries: SCIXyDataSeries) {
        let rSeries = surface.renderableSeries
        
        // shift old dataSeries
        rSeries.item(at: 9).dataSeries = rSeries.item(at: 8).dataSeries
        rSeries.item(at: 8).dataSeries = rSeries.item(at: 7).dataSeries
        rSeries.item(at: 7).dataSeries = rSeries.item(at: 6).dataSeries
        rSeries.item(at: 6).dataSeries = rSeries.item(at: 5).dataSeries
        rSeries.item(at: 5).dataSeries = rSeries.item(at: 4).dataSeries
        rSeries.item(at: 4).dataSeries = rSeries.item(at: 3).dataSeries
        rSeries.item(at: 3).dataSeries = rSeries.item(at: 2).dataSeries
        rSeries.item(at: 2).dataSeries = rSeries.item(at: 1).dataSeries
        rSeries.item(at: 1).dataSeries = rSeries.item(at: 0).dataSeries
        
        // use new dataSeries to draw first renderableSeries
        rSeries.item(at: 0).dataSeries = dataSeries
    }
    
    private func addLineRenderableSeries(_ colorCode: UInt32, opacity: Float) {
        let lineRenderSeries = SCIFastLineRenderableSeries()
        lineRenderSeries.opacity = opacity
        lineRenderSeries.strokeStyle = SCISolidPenStyle.init(colorCode: colorCode, thickness: 1)
        
        surface.renderableSeries.add(lineRenderSeries)
    }
}

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