chartd-rb – Encode data for chartd.co

📈 chartd-rb is a Ruby gem for chartd.co, a service from @stathat, that allows you to creat a chart by encoding a dataset into an URL, like so:

https://chartd.co/a.png?w=580&h=180&d0=SRWfaZHLHEDABKKTUYgpqqvws0138eZfaYtwxxsxyst&ymin=94.48&ymax=103.3

The URL can then be used with a simple <img> tag and the resulting chart looks like this:

Installation

Add this line to your application’s Gemfile:

gem 'chartd'

And then execute:

$ bundle

Or install it yourself as:

$ gem install chartd

Usage

# grab some data
data = [1, 2, 3]

# and create a chart
chart = Chartd::Chart.new(data)

chart.url # => https://chartd.co/a.png?d0=Ae9…

Y-Axis Minimum & Maximum

By default chartd uses the minimum and maximum values from your dataset. They can be set explicitly like this:

Chartd::Chart.new(data, min: 0, max: 100)

Multiple Datasets

data can also be a multidimensional array, which will result in the chart having multiple lines. The maximum of datasets to chart is 5.

Example:

# grab some more data
data = [
  [1, 3, 2],
  [5, 3, 4]
]

# and create a chart
chart = Chartd::Chart.new(data)

chart.url # => https://chartd.co/a.png?d0=AeP&d1=9et…

Width & Height

The default dimensions of a chart are 580px x 180px. You can change them using the options parameter:

Chartd::Chart.new(data, options: { w: 2000, h: 1000 })

⚠️ Important: chartd doubles the dimensions of the chart so that the resulting image is @2x, meaning it looks great on retina (high res) screens.

Disabling Y-Axis Labels

The y-axis are both labeled by default. Set ylabel to false when creating a chart to turn that off:

Chartd::Chart.new(data, ylabels: false)

Image Format

While chartd supports both .svg and .png, chartd-rb currently only supports .png. Issue #2 explains why.

Options

The options hash is written directly to the final URL, meaning that all parameters documented on chartd.co can be used. Example:

Chartd::Chart.new(data, options: {
  t: 'My Awesome Chart',
  step: 1,
  hl: 1,
})

I would be happy to accept a PR that integrates some of them (for example the coloring) a little bit more nicely.

Contributing

1. Fork the repository
2. Create a feature branch: git checkout -b your-feature
3. Add your changes
4. Write tests and check coverage report in coverage/index.html
5. Push changes: git push -u origin your-feature
6. Submit a pull request

License

This project is licensed under the MIT license. See the LICENSE file for details.