Python - Creating Bar Graphs with Matplotlib
Python - Creating Bar Graphs with Matplotlib
Submitted by Corey Goldberg on Fri, 23/03/2007 - 21:03.Matplotlib is an open source 2D plotting library for Python. It is very impressive and robust, but the API and documentation is maddeningly difficult to follow.
Here I have provided a function that will create a bar graph [as a png image] from a Python dictionary using the Matplotlib API.
It will auto-size the bars and auto-adjust the axis labels for you. All you need to pass into it is a dictionary data structure (and optionally a graph title and output name).
We start with a Python dictionary like this:
{'A': 70, 'B': 290, 'C': 130}
... and the function will use Matplotlib to create a graph like this:
Here is a sample script that uses my function:
#!/usr/bin/env python
from pylab import *
def main():
my_dict = {'A': 70, 'B': 290, 'C': 130}
bar_graph(my_dict, graph_title='ABC')
def bar_graph(name_value_dict, graph_title='', output_name='bargraph.png'):
figure(figsize=(4, 2)) # image dimensions
title(graph_title, size='x-small')
# add bars
name_value_dict.keys()
for i, key in zip(range(len(name_value_dict)), name_value_dict.keys()):
bar(i + 0.25 , name_value_dict[key], color='red')
# axis setup
xticks(arange(0.65, len(name_value_dict)),
[('%s: %d' % (name, value)) for name, value in
zip(name_value_dict.keys(), name_value_dict.values())],
size='xx-small')
max_value = max(name_value_dict.values())
tick_range = arange(0, max_value, (max_value / 7))
yticks(tick_range, size='xx-small')
formatter = FixedFormatter([str(x) for x in tick_range])
gca().yaxis.set_major_formatter(formatter)
gca().yaxis.grid(which='major')
savefig(output_name)
if __name__ == "__main__":
main()
from pylab import *
def main():
my_dict = {'A': 70, 'B': 290, 'C': 130}
bar_graph(my_dict, graph_title='ABC')
def bar_graph(name_value_dict, graph_title='', output_name='bargraph.png'):
figure(figsize=(4, 2)) # image dimensions
title(graph_title, size='x-small')
# add bars
name_value_dict.keys()
for i, key in zip(range(len(name_value_dict)), name_value_dict.keys()):
bar(i + 0.25 , name_value_dict[key], color='red')
# axis setup
xticks(arange(0.65, len(name_value_dict)),
[('%s: %d' % (name, value)) for name, value in
zip(name_value_dict.keys(), name_value_dict.values())],
size='xx-small')
max_value = max(name_value_dict.values())
tick_range = arange(0, max_value, (max_value / 7))
yticks(tick_range, size='xx-small')
formatter = FixedFormatter([str(x) for x in tick_range])
gca().yaxis.set_major_formatter(formatter)
gca().yaxis.grid(which='major')
savefig(output_name)
if __name__ == "__main__":
main()
enjoy.
-Corey