pygal/svg/charts/pie.py

import math
from operator import add
from lxml import etree
from svg.charts.graph import Graph

def robust_add(a,b):
	"Add numbers a and b, treating None as 0"
	if a is None: a = 0
	if b is None: b = 0
	return a+b

RADIANS = math.pi/180

class Pie(Graph):
	"""
	A presentation-quality SVG pie graph
	
	Synopsis
	========
	
	from svg.charts.pie import Pie
	fields = ['Jan', 'Feb', 'Mar']
	
	data_sales_02 = [12, 45, 21]
	
	graph = Pie(dict(
		height = 500,
		width = 300,
		fields = fields))
	graph.add_data({'data': data_sales_02, 'title': 'Sales 2002'})
	print "Content-type" image/svg+xml\r\n\r\n'
	print graph.burn()
	
	Description
	===========
	This object aims to allow you to easily create high quality
	SVG pie graphs. You can either use the default style sheet
	or supply your own. Either way there are many options which can
	be configured to give you control over how the graph is
	generated - with or without a key, display percent on pie chart,
	title, subtitle etc.
	"""

	"if true, displays a drop shadow for the chart"
	show_shadow	= True
	"Sets the offset of the shadow from the pie chart"
	shadow_offset = 10 

	show_data_labels = False
	"If true, display the actual field values in the data labels"	
	show_actual_values = False
	"If true, display the percentage value of each pie wedge in the data labels"
	show_percent = True
	
	"If true, display the labels in the key"
	show_key_data_labels = True
	"If true, display the actual value of the field in the key"
	show_key_actual_values = True
	"If true, display the percentage value of the wedges in the key"
	show_key_percent = False

	"If true, explode the pie (put space between the wedges)"	
	expanded = False
	"If true, expand the largest pie wedge"
	expand_greatest	= False
	"The amount of space between expanded wedges"
	expand_gap = 10
	
	show_x_labels = False
	show_y_labels = False

	"The font size of the data point labels"
	datapoint_font_size = 12

	stylesheet_names = Graph.stylesheet_names + ['pie.css']

	def add_data(self, data_descriptor):
		"""
		Add a data set to the graph
		
		>>> graph.add_data({data:[1,2,3,4]}) # doctest: +SKIP
		
		Note that a 'title' key is ignored.
		
		Multiple calls to add_data will sum the elements, and the pie will
		display the aggregated data.  e.g.
		
		>>> graph.add_data({data:[1,2,3,4]}) # doctest: +SKIP
		>>> graph.add_data({data:[2,3,5,7]}) # doctest: +SKIP
		
		is the same as:
		
		graph.add_data({data:[3,5,8,11]}) # doctest: +SKIP
		"""
		self.data = map(robust_add, self.data, data_descriptor['data'])

	def add_defs(self, defs):
		"Add svg definitions"
		etree.SubElement(
			defs,
			'filter',
			id='dropshadow',
			width='1.2',
			height='1.2',
			)
		etree.SubElement(
			defs,
			'feGaussianBlur',
			stdDeviation='4',
			result='blur',
			)

	def draw_graph(self):
		"Here we don't need the graph (consider refactoring)"
		pass

	def get_y_labels(self):
		"Definitely consider refactoring"
		return ['']

	def get_x_labels(self):
		"Okay.  I'll refactor after this"
		return ['']

	def keys(self):
		total = reduce(add, self.data)
		percent_scale = 100.0 / total
		def key(field, value):
			result = [field]
			result.append('[%s]' % value)
			if self.show_key_percent:
				percent = str(round((v/total*100))) + '%'
				result.append(percent)
			return ' '.join(result)
		return map(key, self.fields, self.data)
	
	def draw_data(self):
		self.graph = etree.SubElement(self.root, 'g')
		background = etree.SubElement(self.graph, 'g')
		# midground is somewhere between the background and the foreground
		midground = etree.SubElement(self.graph, 'g')
		
		is_expanded = (self.expanded or self.expand_greatest)
		diameter = min(self.graph_width, self.graph_height)
		# the following assumes int(True)==1 and int(False)==0
		diameter -= self.expand_gap * int(is_expanded)
		diameter -= self.datapoint_font_size * int(self.show_data_labels)
		diameter -= 10 * int(self.show_shadow)
		radius = diameter / 2.0

		xoff = (self.width - diameter) / 2
		yoff = (self.height - self.border_bottom - diameter)
		yoff -= 10 * int(self.show_shadow)
		transform = 'translate(%(xoff)s %(yoff)s)' % vars()
		self.graph.set('transform', transform)

		wedge_text_pad = 5
		wedge_text_pad = 20 * int(self.show_percent) * int(self.show_data_labels)

		total = reduce(add, self.data)
		max_value = max(self.data)

		percent_scale = 100.0 / total

		prev_percent = 0
		rad_mult = 3.6 * RADIANS
		for index, (field, value) in enumerate(zip(self.fields, self.data)):
			percent = percent_scale * value
			
			radians = prev_percent * rad_mult
			x_start = radius+(math.sin(radians) * radius)
			y_start = radius-(math.cos(radians) * radius)
			radians = (prev_percent+percent) * rad_mult
			x_end = radius+(math.sin(radians) * radius)
			y_end = radius-(math.cos(radians) * radius)
			percent_greater_fifty = int(percent>=50)
			path = ' '.join((
				"M%(radius)s,%(radius)s",
				"L%(x_start)s,%(y_start)s",
				"A%(radius)s,%(radius)s",
				"0,",
				"%(percent_greater_fifty)s,1,",
				"%(x_end)s %(y_end)s Z"))
			path = path % vars()
			
			wedge = etree.SubElement(
				self.foreground,
				'path',
				{
					'd': path,
					'class': 'fill%s' % (index+1),
				}
				)
			
			translate = None
			tx = 0
			ty = 0
			half_percent = prev_percent + percent / 2
			radians = half_percent * rad_mult
			
			if self.show_shadow:
				shadow = etree.SubElement(
					background,
					'path',
					d=path,
					filter='url(#dropshadow)',
					style='fill: #ccc; stroke: none',
				)
				clear = etree.SubElement(
					midground,
					'path',
					d=path,
					# note, this probably only works when the background
					#  is also #fff
					# consider getting the style from the stylesheet
					style="fill:#fff; stroke:none;",
				)
			
			if self.expanded or (self.expand_greatest and value == max_value):
				tx = (math.sin(radians) * self.expand_gap)
				ty = -(math.cos(radians) * self.expand_gap)
				translate = "translate(%(tx)s %(ty)s)" % vars()
				wedge.set('transform', translate)
				clear.set('transform', translate)
			
			if self.show_shadow:
				shadow_tx = self.shadow_offset + tx
				shadow_ty = self.shadow_offset + ty
				translate = 'translate(%(shadow_tx)s %(shadow_ty)s)' % vars()
				shadow.set('transform', translate)
			
			if self.show_data_labels and value != 0:
				label = []
				if self.show_key_data_labels:
					label.append(field)
				if self.show_actual_values:
					label.append('[%s]' % value)
				if self.show_percent:
					label.append('%d%%' % round(percent))
				label = ' '.join(label)

				msr = math.sin(radians)
				mcr = math.cos(radians)
				tx = radius + (msr * radius)
				ty = radius -(mcr * radius)
				
				if self.expanded or (self.expand_greatest and value == max_value):
				  tx += (msr * self.expand_gap)
				  ty -= (mcr * self.expand_gap)

				label_node = etree.SubElement(
					self.foreground,
					'text',
					{
						'x':str(tx),
						'y':str(ty),
						'class':'dataPointLabel',
						'style':'stroke: #fff; stroke-width: 2;',
					}
				)
				label_node.text = label

				label_node = etree.SubElement(
					self.foreground,
					'text',
					{
						'x':str(tx),
						'y':str(ty),
						'class': 'dataPointLabel',
					}
				)
				label_node.text = label
			
			prev_percent += percent

	def round(self, val, to):
		return round(val,to)