go-chart/README.md

go-chart
========
[![Build Status](https://travis-ci.org/wcharczuk/go-chart.svg?branch=master)](https://travis-ci.org/wcharczuk/go-chart)

Package `chart` is a very simple golang native charting library that supports timeseries and continuous
line charts. 

The v1.0 release has been tagged so things should be more or less stable, if something changes please log an issue.

# Installation

To install `chart` run the following:

```bash
> go get -u github.com/wcharczuk/go-chart
```

Most of the components are interchangeable so feel free to crib whatever you want. 

# Output Examples 

Spark Lines:

![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/_images/tvix_ltm.png)

Single axis:

![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/_images/goog_ltm.png)

Two axis:

![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/_images/two_axis.png)

# Other Chart Types

Pie Chart:

![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/_images/pie_chart.png)

The code for this chart can be found in `_examples/pie_chart/main.go`.

Stacked Bar:

![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/_images/stacked_bar.png)

The code for this chart can be found in `_examples/stacked_bar/main.go`.

# Code Examples

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.

# Usage

Everything starts with the `chart.Chart` object. The bare minimum to draw a chart would be the following:

```golang

import (
    ...
    "bytes"
    ...
    "github.com/wcharczuk/go-chart" //exposes "chart"
)

graph := chart.Chart{
    Series: []chart.Series{
        chart.ContinuousSeries{
            XValues: []float64{1.0, 2.0, 3.0, 4.0},
            YValues: []float64{1.0, 2.0, 3.0, 4.0},
        },
    },
}

buffer := bytes.NewBuffer([]byte{})
err := graph.Render(chart.PNG, buffer)
```

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).

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`.

# API Overview

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
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`.

The best way to see the api in action is to look at the examples in the `./_examples/` directory.

# Design Philosophy

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).

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.

# Contributions

This library is super early but contributions are welcome.