The iOS ECG Monitor Demo shows how to create a simple ECG / EKG Heart Rate Monitor App using SciChart iOS.

In this example, we use a SCIFastLineRenderableSeries with data provided by XyDataSeries. The DataSeries is in FIFO ‘First in first out’ mode so that old points are discarded once a limit of points is reached. Sweeping is achieved by overlaying two series, so that when the trace reaches the right edge, it wraps around again to the beginning.

The app is realtime and smooth, showcasing that SciChart iOS is suitable for use in realtime medical or health tracking applications.

// ECGChartView.m

//******************************************************************************
// SCICHART® Copyright SciChart Ltd. 2011-2018. All rights reserved.
//
// Web: http://www.scichart.com
// Support: support@scichart.com
// Sales:   sales@scichart.com
//
// ECGChartView.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 "ECGChartView.h"
#include "DataManager.h"

static double const TimeInterval = 0.02;

@implementation ECGChartView {
    SCIXyDataSeries * _series0;
    SCIXyDataSeries * _series1;
    NSArray * _sourceData;
    
    NSTimer * _timer;
    int _currentIndex;
    int _totalIndex;
    
    TraceAOrB _whichTrace;
}

- (void)initExample {
    _sourceData = [DataManager loadWaveformData];
    
    id<SCIAxis2DProtocol> xAxis = [SCINumericAxis new];
    xAxis.autoRange = SCIAutoRange_Never;
    xAxis.axisTitle = @"Time (seconds)";
    xAxis.visibleRange = [[SCIDoubleRange alloc] initWithMin:SCIGeneric(0) Max:SCIGeneric(10)];
    
    id<SCIAxis2DProtocol> yAxis = [SCINumericAxis new];
    yAxis.autoRange = SCIAutoRange_Never;
    yAxis.axisTitle = @"Voltage (mV)";
    yAxis.visibleRange = [[SCIDoubleRange alloc] initWithMin:SCIGeneric(-0.5) Max:SCIGeneric(1.5)];
    
    _series0 = [[SCIXyDataSeries alloc] initWithXType:SCIDataType_Double YType:SCIDataType_Double];
    _series0.fifoCapacity = 3850;
    _series1 = [[SCIXyDataSeries alloc] initWithXType:SCIDataType_Double YType:SCIDataType_Double];
    _series1.fifoCapacity = 3850;
    
    SCIFastLineRenderableSeries * rSeries1 = [SCIFastLineRenderableSeries new];
    rSeries1.dataSeries = _series0;
    SCIFastLineRenderableSeries * rSeries2 = [SCIFastLineRenderableSeries new];
    rSeries2.dataSeries = _series1;
    
    [SCIUpdateSuspender usingWithSuspendable:self.surface withBlock:^{
        [self.surface.xAxes add:xAxis];
        [self.surface.yAxes add:yAxis];
        [self.surface.renderableSeries add:rSeries1];
        [self.surface.renderableSeries add:rSeries2];
        
        [SCIThemeManager applyDefaultThemeToThemeable:self.surface];
    }];
}

- (void)appendData:(NSTimer *)timer {
    for (int i = 0; i < 10; i++) {
        [self appendPoint:400];
    }
}

- (void)appendPoint:(double)sampleRate {
    if (_currentIndex >= _sourceData.count) {
        _currentIndex = 0;
    }
    
    // Get the next voltage and time, and append to the chart
    double voltage = [(NSNumber *)[_sourceData objectAtIndex:_currentIndex] doubleValue];
    double time = fmod((_totalIndex / sampleRate), 10.0);
    
    if (_whichTrace == TraceA) {
        [_series0 appendX:SCIGeneric(time) Y:SCIGeneric(voltage)];
        [_series1 appendX:SCIGeneric(time) Y:SCIGeneric(NAN)];
    } else {
        [_series0 appendX:SCIGeneric(time) Y:SCIGeneric(NAN)];
        [_series1 appendX:SCIGeneric(time) Y:SCIGeneric(voltage)];
    }
    
    _currentIndex++;
    _totalIndex++;
    
    if (_totalIndex % 4000 == 0) {
        _whichTrace = _whichTrace == TraceA ? TraceB : TraceA;
    }
}

- (void)willMoveToWindow:(UIWindow *)newWindow {
    [super willMoveToWindow: newWindow];
    if(_timer == nil){
        _timer = [NSTimer scheduledTimerWithTimeInterval:TimeInterval target:self selector:@selector(appendData:) userInfo:nil repeats:YES];
    } else {
        [_timer invalidate];
        _timer = nil;
    }
}

@end

// ECGChartView.swift

//******************************************************************************
// SCICHART® Copyright SciChart Ltd. 2011-2018. All rights reserved.
//
// Web: http://www.scichart.com
// Support: support@scichart.com
// Sales:   sales@scichart.com
//
// ECGChartView.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.
//******************************************************************************

enum TraceAOrB {
    case TraceA
    case TraceB
}

class ECGChartView: SingleChartLayout {
    
    let TimeInterval = 0.02;

    var _series0: SCIXyDataSeries = SCIXyDataSeries(xType: .double, yType: .double)
    var _series1: SCIXyDataSeries = SCIXyDataSeries(xType: .double, yType: .double)
    let _sourceData = DataManager.loadWaveformData()
    
    var _timer: Timer!
    var _currentIndex: Int = 0
    var _totalIndex = 0.0
    
    var _whichTrace: TraceAOrB = .TraceA
    
    override func initExample() {
        let xAxis = SCINumericAxis()
        xAxis.autoRange = .never
        xAxis.axisTitle = "Time (seconds)"
        xAxis.visibleRange = SCIDoubleRange(min: SCIGeneric(0), max: SCIGeneric(10))
        
        let yAxis = SCINumericAxis()
        yAxis.autoRange = .never
        yAxis.axisTitle = "Voltage (mV)"
        yAxis.visibleRange = SCIDoubleRange(min: SCIGeneric(-0.5), max: SCIGeneric(1.5))
        
        _series0.fifoCapacity = 3850
        _series1.fifoCapacity = 3850
        
        let rSeries0 = SCIFastLineRenderableSeries()
        rSeries0.dataSeries = _series0;
        let rSeries1 = SCIFastLineRenderableSeries()
        rSeries1.dataSeries = _series1;
        
        SCIUpdateSuspender.usingWithSuspendable(surface) {
            self.surface.xAxes.add(xAxis)
            self.surface.yAxes.add(yAxis)
            self.surface.renderableSeries.add(rSeries0)
            self.surface.renderableSeries.add(rSeries1)
            
            SCIThemeManager.applyDefaultTheme(toThemeable: self.surface)
        }
    }

    @objc fileprivate func appendData() {
        for _ in 0..<10 {
            appendPoint(400)
        }
    }

    fileprivate func appendPoint(_ sampleRate: Double) {
        if _currentIndex >= _sourceData!.count {
            _currentIndex = 0
        }
        
        // Get the next voltage and time, and append to the chart
        let voltage = Double(_sourceData![_currentIndex] as! String)!
        let time = fmod(_totalIndex / sampleRate, 10.0)

        if (_whichTrace == .TraceA) {
            _series0.appendX(SCIGeneric(time), y: SCIGeneric(voltage))
            _series1.appendX(SCIGeneric(time), y: SCIGeneric(Double.nan))
        } else {
            _series0.appendX(SCIGeneric(time), y: SCIGeneric(Double.nan))
            _series1.appendX(SCIGeneric(time), y: SCIGeneric(voltage))
        }
        
        _currentIndex += 1
        _totalIndex += 1
        
        if (Int(_totalIndex) % 4000 == 0) {
            _whichTrace = _whichTrace == .TraceA ? .TraceB : .TraceA;
        }
    }
    
    override func willMove(toSuperview newSuperview: UIView?) {
        super.willMove(toSuperview: newSuperview)
        if _timer == nil {
            _timer = Timer.scheduledTimer(timeInterval: TimeInterval, target: self, selector: #selector(appendData), userInfo: nil, repeats: true)
        } else {
            _timer.invalidate()
            _timer = nil
        }
    }
}

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