This example demonstrates how to use the series value modifier with Xamarin in SciChart. It is a very popular feature for the Financial and Trading applications as this allows you to alwasy see the latest value on a screen, no matter where you scrolled or zoomed in to.

// UsingSeriesValueModifierViewController.cs (Xamarin.iOS)

using System;
using SciChart.iOS.Charting;
using System.Timers;
using UIKit;

namespace Xamarin.Examples.Demo.iOS
{
    [ExampleDefinition("Realtime Series Values on Axis", description: "Demonstrates usage of the SCISeriesValueModifier", icon: ExampleIcon.RealTime)]
    public class UsingSeriesValueModifierViewController : SingleChartViewController<SCIChartSurface>
    {
        private const int FifoCapacity = 100;
        private const double TimerInterval = 20;
        private const double OneOverTimeInteval = 1.0 / TimerInterval;
        private Timer _timer;
        private double _t = 0;

        private readonly XyDataSeries<double, double> _ds1 = new XyDataSeries<double, double> { FifoCapacity = FifoCapacity, SeriesName = "Orange Series" };
        private readonly XyDataSeries<double, double> _ds2 = new XyDataSeries<double, double> { FifoCapacity = FifoCapacity, SeriesName = "Blue Series" };
        private readonly XyDataSeries<double, double> _ds3 = new XyDataSeries<double, double> { FifoCapacity = FifoCapacity, SeriesName = "Green Series" };

        protected override void InitExample()
        {
            var xAxis = new SCINumericAxis
            {
                AutoRange = SCIAutoRange.Always,
                AxisTitle = "Time (Seconds)",
                TextFormatting = "0.0"
            };
            var yAxis = new SCINumericAxis
            {
                AutoRange = SCIAutoRange.Always,
                AxisTitle = "Amplitude (Volts)",
                GrowBy = new SCIDoubleRange(0.1, 0.1),
                TextFormatting = "0.00",
                CursorTextFormatting = "0.00"
            };

            var rSeries1 = new SCIFastLineRenderableSeries { DataSeries = _ds1, StrokeStyle = new SCISolidPenStyle(0xFFFF8C00, 2f) };
            var rSeries2 = new SCIFastLineRenderableSeries { DataSeries = _ds2, StrokeStyle = new SCISolidPenStyle(0xFF4682B4, 2f) };
            var rSeries3 = new SCIFastLineRenderableSeries { DataSeries = _ds3, StrokeStyle = new SCISolidPenStyle(0xFF556B2F, 2f) };

            using (Surface.SuspendUpdates())
            {
                Surface.XAxes.Add(xAxis);
                Surface.YAxes.Add(yAxis);
                Surface.RenderableSeries.Add(rSeries1);
                Surface.RenderableSeries.Add(rSeries2);
                Surface.RenderableSeries.Add(rSeries3);
                Surface.ChartModifiers.Add(new SCILegendModifier { Margins = new UIEdgeInsets(16, 16, 16, 16)});
                Surface.ChartModifiers.Add(new SCISeriesValueModifier());
            }

            Start();
        }

        private void Start()
        {   
            _timer = new Timer(TimerInterval);
            _timer.Elapsed += OnTick;
            _timer.AutoReset = true;
            _timer.Start();
        }

        private void OnTick(object sender, ElapsedEventArgs e)
        {
            InvokeOnMainThread(() =>
            {
                var y1 = 3.0 * Math.Sin(((2 * Math.PI) * 1.4) * _t * 0.02);
                var y2 = 2.0 * Math.Cos(((2 * Math.PI) * 0.8) * _t * 0.02);
                var y3 = 1.0 * Math.Sin(((2 * Math.PI) * 2.2) * _t * 0.02);

                _ds1.Append(_t, y1);
                _ds2.Append(_t, y2);
                _ds3.Append(_t, y3);

                _t += OneOverTimeInteval;
            });
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            Reset();
        }

        private void Reset()
        {
            _timer.Stop();
            _timer.Elapsed -= OnTick;
            _timer = null;

            using (Surface.SuspendUpdates())
            {
                _t = 0;

                _ds1.Clear();
                _ds2.Clear();
                _ds3.Clear();
            }
        }
    }
}

// UsingSeriesValueModifierFragment.cs (Xamarin.Android)

using System;
using System.Timers;
using Android.Views;
using SciChart.Charting.Model.DataSeries;
using SciChart.Charting.Modifiers;
using SciChart.Charting.Visuals;
using SciChart.Charting.Visuals.Axes;
using SciChart.Charting.Visuals.RenderableSeries;
using SciChart.Data.Model;
using SciChart.Drawing.Common;
using Xamarin.Examples.Demo.Droid.Extensions;
using Xamarin.Examples.Demo.Droid.Fragments.Base;

namespace Xamarin.Examples.Demo.Droid.Fragments.Examples
{
    [ExampleDefinition("Realtime Series Values on Axis", description: "Demonstrates usage of the SCISeriesValueModifier", icon: ExampleIcon.RealTime)]
    public class UsingSeriesValueModifierFragment : ExampleBaseFragment
    {
        private const int FifoCapacity = 100;
        private const long TimerInterval = 20;
        private const double OneOverTimeInteval = 1.0 / TimerInterval;

        public override int ExampleLayoutId => Resource.Layout.Example_Single_Chart_Fragment;

        private SciChartSurface Surface => View.FindViewById<SciChartSurface>(Resource.Id.chart);

        private readonly XyDataSeries<double, double> _ds1 = new XyDataSeries<double, double> { FifoCapacityValue = FifoCapacity, SeriesName = "Orange Series" };
        private readonly XyDataSeries<double, double> _ds2 = new XyDataSeries<double, double> { FifoCapacityValue = FifoCapacity, SeriesName = "Blue Series" };
        private readonly XyDataSeries<double, double> _ds3 = new XyDataSeries<double, double> { FifoCapacityValue = FifoCapacity, SeriesName = "Green Series" }; 

        private double _t = 0;
        private readonly object _syncRoot = new object();
        private Timer _timer;

        protected override void InitExample()
        {
            var xAxis = new NumericAxis(Activity)
            {
                AutoRange = AutoRange.Always,
                AxisTitle = "Time (Seconds)",
                TextFormatting = "0.0"
            };
            var yAxis = new NumericAxis(Activity)
            {
                AutoRange = AutoRange.Always,
                AxisTitle = "Amplitude (Volts)",
                GrowBy = new DoubleRange(0.1, 0.1),
                TextFormatting = "0.00",
                CursorTextFormatting = "0.00"
            };

            var rs1 = new FastLineRenderableSeries { DataSeries = _ds1, StrokeStyle = new SolidPenStyle(0xFFFF8C00, 2f.ToDip(Activity)) };
            var rs2 = new FastLineRenderableSeries { DataSeries = _ds2, StrokeStyle = new SolidPenStyle(0xFF4682B4, 2f.ToDip(Activity)) };
            var rs3 = new FastLineRenderableSeries { DataSeries = _ds3, StrokeStyle = new SolidPenStyle(0xFF556B2F, 2f.ToDip(Activity)) };

            var legendModifier = new LegendModifier(Activity);
            legendModifier.SetLegendPosition(GravityFlags.Top | GravityFlags.Left | GravityFlags.Bottom | GravityFlags.Right, 16);

            using (Surface.SuspendUpdates())
            {
                Surface.XAxes.Add(xAxis);
                Surface.YAxes.Add(yAxis);
                Surface.RenderableSeries.Add(rs1);
                Surface.RenderableSeries.Add(rs2);
                Surface.RenderableSeries.Add(rs3);
                Surface.ChartModifiers.Add(legendModifier);
                Surface.ChartModifiers.Add(new SeriesValueModifier());
            }
            Start();
        }

        private void Start()
        {
            _timer = new Timer(TimerInterval);
            _timer.Elapsed += OnTick;
            _timer.AutoReset = true;
            _timer.Start();
        }

        private void OnTick(object sender, ElapsedEventArgs e)
        {
            lock (_syncRoot)
            {
                var y1 = 3.0 * Math.Sin(((2 * Math.PI) * 1.4) * _t * 0.02);
                var y2 = 2.0 * Math.Cos(((2 * Math.PI) * 0.8) * _t * 0.02);
                var y3 = 1.0 * Math.Sin(((2 * Math.PI) * 2.2) * _t * 0.02);

                _ds1.Append(_t, y1);
                _ds2.Append(_t, y2);
                _ds3.Append(_t, y3);

                _t += OneOverTimeInteval;
            }
        }

        public override void OnDestroyView()
        {
            base.OnDestroyView();

            Reset();
        }

        private void Reset()
        {
            _timer.Stop();
            _timer.Elapsed -= OnTick;
            _timer = null;

            using (Surface.SuspendUpdates())
            {
                _t = 0;

                _ds1.Clear();
                _ds2.Clear();
                _ds3.Clear();
            }
        }

        public override void InitExampleForUiTest()
        {
            base.InitExampleForUiTest();

            lock (_syncRoot)
            {
                Reset(); 

                var random = new Random(42);
                for (var i = 0; i < FifoCapacity; i++)
                {
                    lock (_syncRoot)
                    {
                        var y1 = 3.0 * Math.Sin(((2 * Math.PI) * 1.4) * _t * 0.02);
                        var y2 = 2.0 * Math.Cos(((2 * Math.PI) * 0.8) * _t * 0.02);
                        var y3 = 1.0 * Math.Sin(((2 * Math.PI) * 2.2) * _t * 0.02);

                        _ds1.Append(_t, y1);
                        _ds2.Append(_t, y2);
                        _ds3.Append(_t, y3);

                        _t += OneOverTimeInteval;
                    }
                }
            }
        }
    }
}

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