chrisdinn/Playfair

=Playfair

Playfair is a Ruby data visualization library that seeks to make graphing and charting easy.

== Installation

Using Rubygems, it's easy:

gem install playfair

== Usage

=== Creating a chart

First things first: create a chart. Once created, you can render it into a bar chart, a line
chart or a pie chart. However, before you render them, charts are just an organized set of values.

Create a chart like this:

chart = Playfair::Chart.new do
  value 90, "Firefox"
  value 55, "IE"
end

=== Rendering

By default, Playfair uses a lean and mean Google Charts API (http://code.google.com/apis/chart/) renderer.
It returns a url pointing to an image of your data, charted.

==== Pie Chart

Render that chart to a Google Chart API pie chart url

chart.render :pie_chart
=> "http://chart.apis.google.com/chart?cht=p&chd=t:90,55&chxt=x,y&chxl=0:|Firefox|IE&chs=330x200"

==== Bar Chart

Render to a Google Chart API bar chart url

chart.render :bar_chart
=> "http://chart.apis.google.com/chart?cht=bvs&chd=t:90,55&chxt=x,y&chxl=0:|Firefox|IE&chs=330x200"

==== Line Chart

You can create a simple line chart, too.

chart = Playfair::Chart.new do
  value 90, "5am"
  value 55, "10am"
  value 77, "3pm"
  value 65, "9pm"
  value 74, "1am"
end
chart.title = "Internet users"

chart.render :line_chart
=> "http://chart.apis.google.com/chart?cht=lc&chd=t:90,55,77,65,74&chxt=x,y&chxl=0:|5am|10am|3pm|9pm..."

==== Chart size

You can render your chart any size you want.

chart.render :bar_chart, :width => 500, :height => 500
=> "http://chart.apis.google.com/chart?cht=bvs&chd=t:90,55&chxt=x,y&chxl=0:|Firefox|IE&chs=500x500"

=== Other chart renderers

You can also render bar and line charts to pdf files use the nascent Playfair::PDFRenderer. To use:

chart = Playfair::Chart.new do
  value 90, "5am"
  value 55, "10am"
  value 77, "3pm"
  value 65, "9pm"
  value 74, "1am"
end
chart.title = "Internet users"
chart.renderer = Playfair::PDFRenderer

chart.render :bar_chart, :to => "test_chart.pdf"

== Who?

Between 1786 and 1801 William Playfair (http://en.wikipedia.org/wiki/William_Playfair) invented the Bar, Line,
and Pie charts. Pretty wicked.

For a more modern take on charting, read Edward Tufte (http://en.wikipedia.org/wiki/Edward_Tufte). My
favourite is The Visual Display of Quantitative Information (http://www.edwardtufte.com/tufte/books_vdqi).

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