Donut chart generator

donutchart.rb

def donut(data, size, thickness, background='#fff')
	cx = cy = size / 2
	radius = size / 2 - 2
	sum = data.values.inject(:+)

	dx = 0
	dy = -radius
	angle = -90
	paths = ''

	data.each do |klass, value|
		_angle = angle + value / (sum / 360.0)
		x = Math.cos(_angle * Math::PI / 180) * radius
		y = Math.sin(_angle * Math::PI / 180) * radius
		ax, ay = cx + x, cy + y
		adx, ady = cx + dx, cy + dy

		paths << %Q{
			<path
				class="#{klass} donut__slice"
				d="
					M#{cx},#{cy}
					L#{adx},#{ady}
					A#{radius},#{radius} 0 %{laf},1 #{ax},#{ay}z
				"
			/>
		} % {laf: value > sum / 2.0 ? 1 : 0}

		dx, dy = x, y
		angle = _angle
	end

	paths << %Q{
		<circle
			class="donut__hole"
			cx="#{cx}" cy="#{cy}" r="%{radius}"
			fill="#{background}"
		/>
	} % {radius: radius - thickness}

	%Q{
		<svg width="#{size}px" height="#{size}px" class="donut" xmlns="http://www.w3.org/2000/svg">
			#{paths}
		</svg>
	}
end