2. Pygal draws stacked histogram, stacked line chart, point chart and pie chart

1) overlay

• The second group of data in the stack chart will be superimposed on the first group of data, and the accumulation effect of the two groups of data can be seen. The same can be seen for other groups of data.

(1) stacked histogram: Pygal.StackedBar()

import pygal
import random

# data
year_data = [str(i) for i in range(2011, 2020)]
banana_data = [random.randint(20,40)*1000 for i in range(1, 10)]
apple_data = [random.randint(35,60)*1000 for i in range(1, 10)]

garph = pygal.StackedBar()    # Create graph (overlay histogram)

# Add data
garph.add('Annual sales of bananas', banana_data)
garph.add('Apple's annual sales', apple_data)

garph.x_labels = year_data            # Set X-axis scale
garph.y_label_rotation = 45           # Set how many degrees the label rotates on the Y axis

garph.title = 'Sales analysis of banana and apple over the years'  # Set graph title
garph.x_title = 'Particular year'                 # Set X-axis title
garph.y_title = 'Sales volume (ton)'            # Set Y-axis title

garph.legend_at_bottom = True         # Set legend location (below)

garph.margin = 35    # Set margins (margin [bottom], margin [top], margin [left], margin [right)

garph.show_x_guides = True    # Show gridlines for X axis
garph.show_y_guides = True    # Show gridlines on Y axis

garph.render_to_file('fruit.svg')    # Output to picture file

(2) stacked line chart: pygal. Stackeline()

garph = pygal.StackedLine()    # Create graph (overlay line graph)

garph.add('Annual sales of bananas', banana_data)
garph.add('Apple's annual sales', apple_data)

garph.x_labels = year_data
garph.y_label_rotation = 45

garph.title = 'Sales analysis of banana and apple over the years'
garph.x_title = 'Particular year'
garph.y_title = 'Sales volume (ton)'

garph.legend_at_bottom = True

garph.margin = 35

garph.show_x_guides = True
garph.show_y_guides = True

garph.render_to_file('fruit.svg')

(3) horizontal overlay

• HorizontalStackedBar(): horizontal stacked histogram
• Horizontalstackeline(): horizontal stacked line chart

2) point graph: pygal.Dot ()

• Point graphs use the size of points (circles) to represent the size of values

garph = pygal.Dot()     # Create graph (point graph)

garph.add('Annual sales of bananas', banana_data)
garph.add('Apple's annual sales', apple_data)

garph.x_labels = year_data

garph.title = 'Sales analysis of banana and apple over the years'
garph.x_title = 'Particular year'
garph.y_title = 'Fruit types'

garph.y_label_rotation = 45

garph.legend_at_bottom = True

garph.margin = 35

garph.show_x_guides = True
garph.show_y_guides = False

garph.render_to_file('fruit.svg')

3) pie chart

(1) traditional pie chart: pygal.Pie()

import pygal

# Market share of programming languages in August 2018
data = {'Java':0.16881, 'c':0.14996, 'c++':0.07471, 'python':0.06992, 'VB.net':0.04762, 'c#':0.03541, 'PHP':0.02925, 'JavaScript':0.02411, 'SQL':0.06316, 'Assembly language':0.01409, 'Other':0.36326}


graph = pygal.Pie()    # Create a chart (pie chart)

# Add data
for k in data.keys():
    graph.add(k, data[k])
    
graph.title = '2018 Market share of programming languages in August'     # Set graph title

graph.legend_at_bottom = True                  # Set legend location (below)

graph.render_to_file('language.svg')            # Output to picture file

(2) hollow pie chart

• Inner radius: set the inner radius of pie chart

graph = pygal.Pie()

for k in data.keys():
    graph.add(k, data[k])
    
graph.title = '2018 Market share of programming languages in August'

graph.legend_at_bottom = True

graph.inner_radius = 0.5     # Hollow pie chart

graph.render_to_file('language.svg')

(3) semicircle pie

• half_pie: set to True

graph = pygal.Pie()

for k in data.keys():
    graph.add(k, data[k])
    
graph.title = '2018 Market share of programming languages in August'

graph.legend_at_bottom = True

graph.half_pie = True    # Half circle pie chart

graph.render_to_file('language.svg')