112 lines
3.5 KiB
Markdown
112 lines
3.5 KiB
Markdown
go-chart
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========
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[](https://travis-ci.org/wcharczuk/go-chart)
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Package `chart` is a very simple golang native charting library that supports timeseries and continuous
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line charts.
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The API is still in a bit of flux, so it is adviseable to wait until I tag a v1.0 release before using
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in a production capacity.
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# Installation
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To install `chart` run the following:
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```bash
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> go get -u github.com/wcharczuk/go-chart
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```
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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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The chart code to produce the above is as follows:
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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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# Alternate Usage
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You can alternately turn a bunch of features off and constrain the proportions to something like a spark line:
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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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# Design Philosophy
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I wanted to make a charting library that used only native golang, that could be stood up on a server (i.e. it had built in fonts).
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The goal with the API itself is to have the "zero value be useful", and to require the user to not code more than they absolutely needed.
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# Contributions
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This library is super early but contributions are welcome.
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