Htykuut

Is there any way to plot a bar plot using matplotlib using data directly from a dict?

My dict looks like this:

D = {u'Label1':26, u'Label2': 17, u'Label3':30}

I was expecting

fig = plt.figure(figsize=(5.5,3),dpi=300)

ax = fig.add_subplot(111)

bar = ax.bar(D,range(1,len(D)+1,1),0.5)

to work, but it does not.

Here is the error:

>>> ax.bar(D,range(1,len(D)+1,1),0.5)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes.py", line 4904, in bar

    self.add_patch(r)

  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes.py", line 1570, in add_patch

    self._update_patch_limits(p)

  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes.py", line 1588, in _update_patch_limits

    xys = patch.get_patch_transform().transform(vertices)

  File "/usr/local/lib/python2.7/site-packages/matplotlib/patches.py", line 580, in get_patch_transform

    self._update_patch_transform()

  File "/usr/local/lib/python2.7/site-packages/matplotlib/patches.py", line 576, in _update_patch_transform

    bbox = transforms.Bbox.from_bounds(x, y, width, height)

  File "/usr/local/lib/python2.7/site-packages/matplotlib/transforms.py", line 786, in from_bounds

    return Bbox.from_extents(x0, y0, x0 + width, y0 + height)

TypeError: coercing to Unicode: need string or buffer, float found

You can do it in two lines by first plotting the bar chart and then setting the appropriate ticks:

import matplotlib.pyplot as plt



D = {u'Label1':26, u'Label2': 17, u'Label3':30}



plt.bar(range(len(D)), list(D.values()), align='center')

plt.xticks(range(len(D)), list(D.keys()))

# # for python 2.x:

# plt.bar(range(len(D)), D.values(), align='center')  # python 2.x

# plt.xticks(range(len(D)), D.keys())  # in python 2.x



plt.show()

Note that the penultimate line should read plt.xticks(range(len(D)), list(D.keys())) in python3, because D.keys() returns a generator, which matplotlib cannot use directly.

For future reference, the above code does not work with Python 3. For Python 3, the D.keys() needs to be converted to a list.

import matplotlib.pyplot as plt



D = {u'Label1':26, u'Label2': 17, u'Label3':30}



plt.bar(range(len(D)), D.values(), align='center')

plt.xticks(range(len(D)), list(D.keys()))



plt.show()

The best way to implement it using matplotlib.pyplot.bar(range, height, tick_label) where the range provides scalar values for the positioning of the corresponding bar in the graph. tick_label does the same work as xticks(). One can replace it with an integer also and use multiple plt.bar(integer, height, tick_label). For detailed information please refer the documentation.

import matplotlib.pyplot as plt



data = {'apple': 67, 'mango': 60, 'lichi': 58}

names = list(data.keys())

values = list(data.values())



#tick_label does the some work as plt.xticks()

plt.bar(range(len(data)),values,tick_label=names)

plt.savefig('bar.png')

plt.show()

Additionally the same plot can be generated without using range(). But the problem encountered was that tick_label just worked for the last plt.bar() call. Hence xticks() was used for labelling:

data = {'apple': 67, 'mango': 60, 'lichi': 58}

names = list(data.keys())

values = list(data.values())

plt.bar(0,values[0],tick_label=names[0])

plt.bar(1,values[1],tick_label=names[1])

plt.bar(2,values[2],tick_label=names[2])

plt.xticks(range(0,3),names)

plt.savefig('fruit.png')

plt.show()

I often load the dict into a pandas DataFrame then use the plot function of the DataFrame.

Here is the one-liner:

pandas.DataFrame(D, index=['quantity']).plot(kind='bar')

It's a little simpler than most answers here suggest:

import matplotlib.pyplot as plt



D = {u'Label1':26, u'Label2': 17, u'Label3':30}

plt.bar(*zip(*D.items()))

plt.show()