examples, some fixes
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Will Charczuk
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210
README.md
210
README.md
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@ -17,178 +17,68 @@ To install `chart` run the following:
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Most of the components are interchangeable so feel free to crib whatever you want.
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# Usage
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# Ouptut Examples
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Spark Lines:
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The chart code to produce the above is as follows:
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Single axis:
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```go
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// note this assumes that xvalues and yvalues
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// have been pulled from a pricing service.
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graph := chart.Chart{
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Width: 1024,
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Height: 400,
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YAxis: chart.YAxis {
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Style: chart.Style{
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Show: true,
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},
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},
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XAxis: chart.XAxis {
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Style: chart.Style{
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Show: true,
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},
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},
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Series: []chart.Series{
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chart.TimeSeries{
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XValues: xvalues,
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YValues: yvalues,
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Style: chart.Style {
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FillColor: chart.DefaultSeriesStrokeColors[0].WithAlpha(64),
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},
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},
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chart.AnnotationSeries{
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Name: "Last Value",
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Style: chart.Style{
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Show: true,
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StrokeColor: chart.DefaultSeriesStrokeColors[0],
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},
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Annotations: []chart.Annotation{
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chart.Annotation{
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X: chart.TimeToFloat64(xvalues[len(xvalues)-1]),
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Y: yvalues[len(yvalues)-1],
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Label: chart.FloatValueFormatter(yvalues[len(yvalues)-1]),
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},
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},
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},
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},
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}
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graph.Render(chart.PNG, buffer) //thats it!
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```
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The key areas to note are that we have to explicitly turn on two features, the axes and add the last value label annotation series. When calling `.Render(..)` we add a parameter, `chart.PNG` that tells the renderer to use a raster renderer. Another option is to use `chart.SVG` which will use the vector renderer and create an svg representation of the chart.
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Two axis:
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# Alternate Usage
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You can alternately leave a bunch of features turned off and constrain the proportions to something like a spark line:
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Simple Moving Average:
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The code to produce the above would be:
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```go
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// note this assumes that xvalues and yvalues
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// have been pulled from a pricing service.
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graph := chart.Chart{
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Width: 1024,
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Height: 100,
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Series: []chart.Series{
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chart.TimeSeries{
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XValues: xvalues,
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YValues: yvalues,
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},
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},
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}
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graph.Render(chart.PNG, buffer)
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```
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# 2 Y-Axis Charts
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It is also possible to draw series against 2 separate y-axis with their own ranges (usually good for comparison charts).
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In order to map the series to an alternate axis make sure to set the `YAxis` property of the series to `YAxisSecondary`.
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```go
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graph := chart.Chart{
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Title: stock.Name,
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TitleStyle: chart.Style{
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Show: false,
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},
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Width: width,
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Height: height,
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XAxis: chart.XAxis{
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Style: chart.Style{
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Show: true,
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},
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},
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YAxis: chart.YAxis{
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Style: chart.Style{
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Show: true,
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},
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},
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Series: []chart.Series{
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chart.TimeSeries{
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Name: "vea",
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XValues: vx,
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YValues: vy,
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Style: chart.Style{
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Show: true,
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StrokeColor: chart.GetDefaultSeriesStrokeColor(0),
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FillColor: chart.GetDefaultSeriesStrokeColor(0).WithAlpha(64),
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},
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},
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chart.TimeSeries{
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Name: "spy",
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XValues: cx,
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YValues: cy,
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YAxis: chart.YAxisSecondary, // key (!)
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Style: chart.Style{
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Show: true,
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StrokeColor: chart.GetDefaultSeriesStrokeColor(1),
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FillColor: chart.GetDefaultSeriesStrokeColor(1).WithAlpha(64),
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},
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},
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chart.AnnotationSeries{
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Name: fmt.Sprintf("%s - Last Value", "vea"),
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Style: chart.Style{
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Show: true,
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StrokeColor: chart.GetDefaultSeriesStrokeColor(0),
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},
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Annotations: []chart.Annotation{
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chart.Annotation{
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X: float64(vx[len(vx)-1].Unix()),
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Y: vy[len(vy)-1],
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Label: fmt.Sprintf("%s - %s", "vea", chart.FloatValueFormatter(vy[len(vy)-1])),
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},
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},
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},
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chart.AnnotationSeries{
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Name: fmt.Sprintf("%s - Last Value", "goog"),
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Style: chart.Style{
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Show: true,
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StrokeColor: chart.GetDefaultSeriesStrokeColor(1),
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},
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YAxis: chart.YAxisSecondary, // key (!)
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Annotations: []chart.Annotation{
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chart.Annotation{
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X: float64(cx[len(cx)-1].Unix()),
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Y: cy[len(cy)-1],
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Label: fmt.Sprintf("%s - %s", "goog", chart.FloatValueFormatter(cy[len(cy)-1])),
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},
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},
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},
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},
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}
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graph.Render(chart.PNG, buffer)
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```
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# Moving Averages
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You can now also graph a moving average of a series using a special `MovingAverageSeries` that takes an `InnerSeries` as a required argument.
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There is a helper method, `GetLastValue` on the `MovingAverageSeries` to aid in creating a last value annotation for the series.
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# More Intense Technical Analysis
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You can also have series that produce two values, i.e. a series that implements `BoundedValueProvider` and the `GetBoundedValue(int)(x,y1,y2 float64)` method. An example of a `BoundedValueProvider` is the included `BollingerBandsSeries`.
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Bollinger Bounds:
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Like the `MovingAverageSeries` this series takes an `InnerSeries` argument as required, and defaults to 10 samples and a `K` value of 2.0 (or two standard deviations in either direction).
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# Code Examples
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Actual chart configurations and examples can be found in the `./examples/` directory. They are web servers, so start them with `go run main.go` then access `http://localhost:8080` to see the output.
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# Usage
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Everything starts with the `chart.Chart` object. The bare minimum to draw a chart would be the following:
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```golang
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import (
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...
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"bytes"
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...
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"github.com/wcharczuk/go-chart" //exposes "chart"
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)
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graph := chart.Chart{
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Series: []chart.Series{
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chart.ContinuousSeries{
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XValues: []float64{1.0, 2.0, 3.0, 4.0},
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YValues: []float64{1.0, 2.0, 3.0, 4.0},
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},
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},
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}
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buffer := bytes.NewBuffer([]byte{})
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err := graph.Render(chart.PNG, buffer)
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```
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Explanation of the above: A `chart` can have many `Series`, a `Series` is a collection of things that need to be drawn according to the X range and the Y range(s).
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Here, we have a single series with x range values as float64s, rendered to a PNG. Note; we can pass any type of `io.Writer` into `Render(...)`, meaning that we can render the chart to a file or a resonse or anything else that implements `io.Writer`.
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# API Overview
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Everything on the `chart.Chart` object has defaults that can be overriden. Whenever a developer sets a property on the chart object, it is to be assumed that value will be used instead of the default. One complication here
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is any object's root `chart.Style` object (i.e named `Style`) and the `Show` property specifically, if any other property is set and the `Show` property is unset, it is assumed to be it's default value of `False`.
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The best way to see the api in action is to look at the examples in the `./examples/` directory.
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# Design Philosophy
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