~/cartesianChart/scatterseries.md

Scatter Series Props

This article do not include all the properties of the Scatter Series Props class, it only highlights some features, to explore the full object checkout the API explorer

Name property

The name property is a string identifier that is normally used in tooltips and legends to display the data name, if this property is not set, then the library will generate a name for the series that by default is called "Series 1" when it is the first series in the series collection, "Series 2" when it is the second series in the series collection, "Series 3" when it is the third series in the series collection, and so on a series n will be named "Series n".

SeriesCollection = new ISeries[]
{
    new ScatterSeriesProps<int>
    {
        Values = new []{ 2, 5, 4, 2, 6 },
        Name = "Income", // mark
        Stroke = null
    },
    new ScatterSeriesProps<int>
    {
        Values = new []{ 3, 7, 2, 9, 4 },
        Name = "Outcome", // mark
        Stroke = null
    }
};

Values property

The Values property is of type IEnumerable<T>, this means that you can use any object that implements the IEnumerable<T> interface, such as Array, List<T> or ObservableCollection<T>, this property contains the data to plot, you can use any type as the generic argument (<T>) as soon as you let the library how to handle it, the library already knows how to handle multiple types, but you can register any type and teach the library how to handle any object in a chart, for more information please see the mappers article.

var series1 = new ScatterSeriesProps<int>
{
    Values = new List<int> { 2, 1, 3 }
};

// == Update the chart when a value is added, removed or replaced  == // mark
// using ObservableCollections allows the chart to update
// every time you add a new element to the values collection
// (not needed in Blazor, it just... updates)
var series2 = new ScatterSeriesProps<double>
{
    Values = new ObservableCollection<double> { 2, 1, 3 }
}
series2.add(4); // and the chart will animate the change!

// == Update the chart when a property in our collection changes  == // mark
// if the object implements INotifyPropertyChanged, then the chart will
// update automatically when a property changes, the library already provides
// many 'ready to go' objects such as the ObservableValue class.
var observableValue =  new ObservableValue(5);
var series3 = new ScatterSeriesProps<ObservableValue>
{
    Values = new ObservableCollection<ObservableValue> { observableValue },
}
observableValue.Value = 9; // the chart will animate the change from 5 to 9!

// == Passing X and Y coordinates // mark 
// you can indicate both, X and Y using the Observable point class.
// or you could define your own object using mappers.
var series4 = new ScatterSeriesProps<ObservablePoint>
{
    Values = new ObservableCollection<ObservablePoint> { new ObservablePoint(2, 6)}
}
// == Custom types and mappers == // mark
// finally you can also use your own object, take a look at the City class.
public class City 
{
    public string Name { get; set; }
    public double Population { get; set; }
}
// we must let the series know how to handle the city class.
// use the Mapping property to build a point from the city class
// you could also register the map globally.
// for more about global mappers info see:
// https://lvcharts.com/docs/winui/2.0.0-beta.330/Overview.Mappers
var citiesSeries = new ScatterSeriesProps<City>
{
    Values = new City[]
    { 
        new City { Name = "Tokio", Population = 9 },
        new City { Name = "New York", Population = 11 },
        new City { Name = "Mexico City", Population = 10 },
    },
    Mapping = (city, point) =>
    {
        // this function will be called for every city in our data collection
        // in this case Tokio, New York and Mexico city
        // it takes the city and the point in the chart liveCharts built for the given city
        // you must map the coordinates to the point

        // use the Population property as the primary value (normally Y)
        point.PrimaryValue = (float)city.Population;

        // use the index of the city in our data collection as the secondary value
        // (normally X)
        point.SecondaryValue = point.Context.Index;
    }
};

Automatic updates do not have a significant performance impact in most of the cases!

Data labels

Data labels are labels for every point in a series, there are multiple properties to customize them, take a look at the following sample:

new ScatterSeriesProps<double>
{
    DataLabelsSize = 20,
    DataLabelsPaint = new SolidColorPaint(SKColors.Blue),
    // all the available positions at:
    // https://lvcharts.com/api/2.0.0-beta.330/LiveChartsCore.Measure.DataLabelsPosition
    DataLabelsPosition = LiveChartsCore.Measure.DataLabelsPosition.Top,
    // The DataLabelsFormatter is a function 
    // that takes the current point as parameter
    // and returns a string.
    // in this case we returned the PrimaryValue property as currency
    DataLabelsFormatter = (point) => point.PrimaryValue.ToString("C2"),
    Values = new ObservableCollection<double> { 2, 1, 3, 5, 3, 4, 6 },
    Fill = null
}

The previous series will result in the following chart:

image

Stroke property

If the stroke property is not set, then LiveCharts will create it based on the series position in your series collection and the current theme.

image

Series = new ISeries[]
{
    new ScatterSeries<ObservablePoint>
    {
        Stroke = new SolidColorPaint(SKColors.Blue) { StrokeThickness = 4 }, // mark
        Fill = null,
        Values = new ObservableCollection<ObservablePoint>
        {
            new ObservablePoint(2.2, 5.4),
            new ObservablePoint(4.5, 2.5),
            new ObservablePoint(4.2, 7.4),
            ...
        }
    }
};

Paints can create gradients, dashed lines and more, if you need help using the Paint instances take a look at the Paints article.

Fill property

If the fill property is not set, then LiveCharts will create it based on the series position in your series collection and the current theme.

image

Series = new ISeries[]
{
    new ScatterSeries<ObservablePoint>
    {
        Fill = new SolidColorPaint(SKColors.Blue), // mark
        Stroke = null,
        Values = new ObservableCollection<ObservablePoint>
        {
            new ObservablePoint(2.2, 5.4),
            new ObservablePoint(4.5, 2.5),
            new ObservablePoint(4.2, 7.4),
            ...
        }
    }
};

Paints can create gradients, dashed lines and more, if you need help using the Paint instances take a look at the Paints article.

GeometrySize property

Determines the size of the geometry, if this property is not set, then the library will decide it based on the theme.

image


var r = new Random();
var values1 = new ObservableCollection<ObservablePoint>();
var values2 = new ObservableCollection<ObservablePoint>();

for (var i = 0; i < 20; i++)
{
    values1.Add(new ObservablePoint(r.Next(0, 20), r.Next(0, 20)));
    values2.Add(new ObservablePoint(r.Next(0, 20), r.Next(0, 20)));
}

Series = new ISeries[]
{
    new ScatterSeries<ObservablePoint, RectangleGeometry>
    {
        Values = values1,
        GeometrySize = 10, // mark
    },
    new ScatterSeries<ObservablePoint, CircleGeometry>
    {
        Values = values2,
        GeometrySize = 30 // mark
    }
};

MinGeometrySize property

This property specifies the minimum size a geometry can take when the Weight plane is enabled, to enable this plane you could use the WeightedPoint class, the library is ready to plot this instance, alternatively you can register a new type using mappers, and use the TertiaryValue property of the ChartPoint instance to specify the weight of each point.

Notice in the following image how every shape has a different size, the size of each geometry represents the Weight of each point, in this case the weight takes a random integer from 0 to 20, so when the Weight is 0 the size of the geometry will be 15 pixels as specified in the MinGeometrySize property, when the Weight is 20 the geometry size will be 40 defined by the GeometrySize property, for any Weight between this range the library will interpolate lineally to determine the corresponding size.

image

var r = new Random();
var values1 = new ObservableCollection<WeightedPoint>();
var values2 = new ObservableCollection<WeightedPoint>();

for (var i = 0; i < 20; i++)
{
    values1.Add(new WeightedPoint(r.Next(0, 20), r.Next(0, 20), r.Next(0, 20)));
    values2.Add(new WeightedPoint(r.Next(0, 20), r.Next(0, 20), r.Next(0, 20)));
}

Series = new ObservableCollection<ISeries>
{
    new ScatterSeries<WeightedPoint, RoundedRectangleGeometry>
    {
        Values = values1,
        GeometrySize = 40,
        MinGeometrySize = 15 // mark
    },

    new ScatterSeries<WeightedPoint, CircleGeometry>
    {
        Values = values2,
        GeometrySize = 40,
        MinGeometrySize = 15 // mark
    }
};

Plotting custom types

You can teach LiveCharts to plot anything, imagine the case where we have an array of the City class defined bellow:

public class City
{
    public string Name { get; set; }
    public double Population { get; set; }
    public double LandArea { get; set; }
}

You can register this type globally, this means that every time LiveCharts finds a City instance in a chart it will use the mapper we registered, global mappers are unique for a type, if you need to plot multiple properties then you should use local mappers.

// Ideally you should call this when your application starts
// If you need help to decide where to add this code
// please see the installation guide in this docs.

// in this case we have an array of the City class
// we need to compare the Population property of every city in our array

LiveCharts.Configure(config =>
    config
        .HasMap<City>((city, point) =>
        {
            // in this lambda function we take an instance of the City class (see city parameter)
            // and the point in the chart for that instance (see point parameter)
            // LiveCharts will call this method for every instance of our City class array,
            // now we need to populate the point coordinates from our City instance to our point

            // in this case we will use the Population property as our primary value (normally the Y coordinate)
            point.PrimaryValue = (float)city.Population;

            // then the secondary value (normally the X coordinate)
            // will be the index of the given dog class in our array
            point.SecondaryValue = point.Context.Index;

            // but you can use another property of the city class as the X coordinate
            // for example lets use the LandArea property to create a plot that compares
            // Population and LandArea in chart:

            // point.SecondaryValue = (float)city.LandArea;

            // OPTIONAL
            // Scatter series supports "weight" for every point
            // The weight creates different geometry sizes for every point
            // based on this value.
            // the sizes of the geometries depend on MinGeometrySize to GeometrySize properties.
            point.TertiaryValue = (float)city.LandArea;
        })
        .HasMap<Foo>(...) // you can register more types here using our fluent syntax
        .HasMap<Bar>(...)
    );

Now we are ready to plot cities all over our application:

Series = new[]
{
    new ScatterSeries<City>
    {
        Name = "Population",
        TooltipLabelFormatter = (point) => $"{point.Model.Name} population: {point.PrimaryValue:N2}M, area: {point.TertiaryValue}KM2",
        GeometrySize = 35,
        MinGeometrySize = 10,
        Values = new[]
        {
            new City { Name = "Tokyo", Population = 4, LandArea = 3 },
            new City { Name = "New York", Population = 6, LandArea = 4 },
            new City { Name = "Seoul", Population = 2, LandArea = 1 },
            new City { Name = "Moscow", Population = 8, LandArea = 7 },
            new City { Name = "Shanghai", Population = 3, LandArea = 2 },
            new City { Name = "Guadalajara", Population = 4, LandArea = 5 }
        }
    }
};

image

Alternatively you could create a local mapper that will only work for a specific series, global mappers will be ignored when the series Mapping property is not null.

var cities = new[]
{
    new City { Name = "Tokyo", Population = 4, LandArea = 3 },
    new City { Name = "New York", Population = 6, LandArea = 4 },
    new City { Name = "Seoul", Population = 2, LandArea = 1 },
    new City { Name = "Moscow", Population = 8, LandArea = 7 },
    new City { Name = "Shanghai", Population = 3, LandArea = 2 },
    new City { Name = "Guadalajara", Population = 4, LandArea = 5 }
};

Series = new[]
{
    // compares Population (Y), LandArea (Y) and Density (weight)
    new LineSeries<City>
    {
        Name = "Population",
        TooltipLabelFormatter = 
            (point) => $"{point.Model.Name} population: {point.PrimaryValue:N2}M, area: {point.SecondaryValue}KM2, density: {point.TertiaryValue:N2}Millions/KM2",
        Values = cities,
        Mapping = (city, point) =>
        {
            point.PrimaryValue = (float)city.Population;
            point.SecondaryValue = (float)city.LandArea;
            point.TertiaryValue = (float)(city.Population/city.LandArea);
        }
    }
};

image

Custom geometries

You can use any geometry to represent a point in a line series.

image

var r = new Random();
var values1 = new ObservableCollection<ObservablePoint>();
var values2 = new ObservableCollection<ObservablePoint>();

for (var i = 0; i < 20; i++)
{
    values1.Add(new ObservablePoint(r.Next(0, 20), r.Next(0, 20)));
    values2.Add(new ObservablePoint(r.Next(0, 20), r.Next(0, 20)));
}

Series = new ObservableCollection<ISeries>
{
    // use the second type argument to specify the geometry to draw for every point
    // there are already many predefined geometries in the
    // LiveChartsCore.SkiaSharpView.Drawing.Geometries namespace
    new ScatterSeries<ObservablePoint, RoundedRectangleGeometry>
    {
        Values = values1,
        Stroke = null,
        GeometrySize = 40,
    },

    // Or Define your own SVG geometry
    new ScatterSeries<ObservablePoint, MyGeomeometry>
    {
        Values = values2,
        GeometrySize = 40
    }
};

Where MyGeometry class is our custom shape, you can draw anything SkiaSharp supports at this point, but in this case we will draw an SVG path, we inherit from SVGPathGeometry, and for performance reasons we use a static variable to parse the SVG path, this ways the parse operation only runs once.

public class MyGeometry : SVGPathGeometry
{
    // the static field is important to prevent the svg path is parsed multiple times // mark
    // Icon from Google Material Icons font.
    // https://fonts.google.com/icons?selected=Material%20Icons%20Outlined%3Amy_location%3A
    public static SKPath svgPath = SKPath.ParseSvgPathData(
        "M12 8c-2.21 0-4 1.79-4 4s1.79 4 4 4 4-1.79 4-4-1.79-4-4-4zm8.94 3c-.46-4.17-3.77-7.48-7.94-7.94V1h-2v2.06C6.83 3.52 3.52 6.83 3.06 " +
        "11H1v2h2.06c.46 4.17 3.77 7.48 7.94 7.94V23h2v-2.06c4.17-.46 7.48-3.77 7.94-7.94H23v-2h-2.06zM12 19c-3.87 0-7-3.13-7-7s3.13-7 7-7 7 " +
        "3.13 7 7-3.13 7-7 7z");

    public MyGeometry()
        : base(svgPath)
    {

    }
}

ZIndex property

Indicates an order in the Z axis, this order controls which series is above or behind.

IsVisible property

Indicates if the series is visible in the user interface.

DataPadding

The data padding is the minimum distance from the edges of the series to the axis limits, it is of type System.Drawing.PointF both coordinates (X and Y) goes from 0 to 1, where 0 is nothing and 1 is the axis tick an axis tick is the separation between every label or separator (even if they are not visible).

If this property is not set, the library will set it according to the series type, take a look at the following samples:

new LineSeries<double>
{
    DataPadding = new System.Drawing.PointF(0, 0),
    Values = new ObservableCollection { 2, 1, 3, 5, 3, 4, 6 },
    GeometryStroke = null,
    GeometryFill = null,
    Fill = null
}

Produces the following result:

image

But you can remove the padding only from an axis, for example:

new LineSeries<double>
{
    DataPadding = new System.Drawing.PointF(0.5f, 0),
    Values = new ObservableCollection<double> { 2, 1, 3, 5, 3, 4, 6 },
    GeometryStroke = null,
    GeometryFill = null,
    Fill = null
}

image

Or you can increase the distance:

new LineSeries<double>
{
    DataPadding = new System.Drawing.PointF(2, 2),
    Values = new ObservableCollection<double> { 2, 1, 3, 5, 3, 4, 6 },
    GeometryStroke = null,
    GeometryFill = null,
    Fill = null
}

image