Writing Algorithms

Charts contain a collection of series, which display data on the chart. To add a chart to an algorithm, create a Chart object and then call the AddChart method.

var chart = new Chart("<chartName>");
AddChart(chart);

chart = Chart("<chartName>")
self.AddChart(chart)

The Chart constructor expects a name argument. The following chart names are reserved:

• Assets Sales Volume
• Exposure
• Alpha Assets
• Alpha Asset Breakdown

A chart series displays data on the chart. To add a series to a chart, create a Series object and then call the AddSeries method.

var series = new Series("<seriesName>");
chart.AddSeries(series);

series = Series("<seriesName>")
chart.AddSeries(series)

Arguments

There are several other headers for the Series constructor.

Series(name, type)
Series(name, type, index)
Series(name, type, index, unit)
Series(name, type, unit)
Series(name, type, unit, color)
Series(name, type, unit, color, symbol)

The following table describes the constructor arguments:

The default Series is a line chart with a "$" unit on index 0.

Names

The Series constructor expects a name argument. If you add a series to one of the default charts, some series names may be reserved. The following table shows the reserved series name for the default charts:

Types

The SeriesType enumeration has the following members:

Index

The series index refers to its position in the chart. If all the series are at index 0, they lay on top of each other. If each series has its own index, each series will be separate on the chart. The following image shows an EMA cross chart with both EMA series set to the same index:

The following image shows the same EMA series, but with the short EMA on index 0 and the long EMA on index 1:

Colors

To view the available Color options, see the Color Struct Properties in the .NET documentation.

Scatter Marker Symbols

The ScatterMarkerSymbol enumeration has the following members:

To add a data point to a chart series, call the Plot method. If you haven't already created a chart and series with the names you pass to the Plot method, the chart and/or series is automatically created.

Plot("<chartName>", "<seriesName>", value);

self.Plot("<chartName>", "<seriesName>", value)

The value argument can be an integer for decimal number. If the chart is a time series, the value is added to the chart using the algorithm time as the x-coordinate.

To plot the current value of indicators, call the Plot method. The method accepts up to four indicators.

// In Initialize
var symbol = AddEquity("SPY");
var smaShort = SMA(symbol, 10);
var smaLong = SMA(symbol, 20);

// In OnData
Plot("<chartName>", smaShort, smaLong)

# In Initialize
symbol = self.AddEquity("SPY")
sma_short = self.SMA(symbol, 10)
sma_long = self.SMA(symbol, 20)

# In OnData
self.Plot("<chartName>", sma_short, sma_long)

To plot all of the values of some indicators, in the Initialize method, call the PlotIndicator method. The method plots each indicator value as the indicator updates. The method accepts up to four indicators.

var symbol = AddEquity("SPY");
var smaShort = SMA(symbol, 10);
var smaLong = SMA(symbol, 20);
PlotIndicator("<chartName>", smaShort, smaLong)

symbol = self.AddEquity("SPY")
sma_short = self.SMA(symbol, 10)
sma_long = self.SMA(symbol, 20)
self.PlotIndicator("<chartName>", sma_short, sma_long)

The following example shows how to plot the daily closing price of SPY with a scatter plot:

public class ChartingDemoAlgorithm : QCAlgorithm
{
    public override void Initialize()
    {
        SetStartDate(2021, 1, 1);
        SetEndDate(2022, 1, 1);
        AddEquity("SPY", Resolution.Daily);
        var chart = new Chart("Price");
        AddChart(chart);
        chart.AddSeries(new Series("SPY", SeriesType.Scatter, "$", Color.Green, ScatterMarkerSymbol.Triangle));
    }

    public override void OnEndOfDay(Symbol symbol)
    {
        Plot("Price", "SPY", Securities[symbol].Price);
    }
}

class ChartingDemoAlgorithm(QCAlgorithm):

    def Initialize(self) -> None:
        self.SetStartDate(2021, 1, 1)
        self.SetEndDate(2022, 1, 1)
        self.AddEquity("SPY", Resolution.Daily)
        chart = Chart("Price")
        self.AddChart(chart)
        chart.AddSeries(Series("SPY", SeriesType.Scatter, "$", Color.Green, ScatterMarkerSymbol.Triangle))

    def OnEndOfDay(self, symbol: Symbol) -> None:
        self.Plot("Price", "SPY", self.Securities[symbol].Price)

To see a full example, run the CustomChartingAlgorithmCustomChartingAlgorithm.

The following table describes where you can access your charts, depending on how to deploy your algorithms:

Location	Algorithm Lab Algorithms	CLI Cloud Algorithms	CLI Local Algorithms
Backtest results page
Live results page
/backtests/read endpoint
/live/read endpoint
ReadBacktest method
ReadLiveAlgorithm method
Local JSON file in your <projectName> / backtests / <timestamp> or <projectName> / live / <timestamp> directory

Custom charts are limited to 4,000 data points. Intensive charting requires hundreds of megabytes of data, which is too much to stream online or display in a web browser. If you exceed the quota, the following message displays:

Exceeded maximum points per chart, data skipped

You can create up to 10 custom chart series per algorithm. If you exceed the quota, your algorithm stops executing and the following message displays:

Exceeded maximum series count: Each backtest can have up to 10 series in total.

In live trading, charts are sampled every one and ten minutes. If you create 1-minute resolution custom charts, the IDE charting will downgrade the granularity and display the 10-minutes sampling after a certain amount of samples.