How do I plot a histogram of this kind of data,
10 apples
3 oranges
6 tomatoes
10 pears
from a text file?
thanks
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Have a look at matplotlib.Felix Kling– Felix Kling2010-09-29 12:06:15 +00:00Commented Sep 29, 2010 at 12:06
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3 Answers
Here's one way you can assign different colors to the bars. It works with even a variable number of bars.
import numpy as np
import pylab
import matplotlib.cm as cm
arr = np.genfromtxt('data', dtype=None)
n = len(arr)
centers = np.arange(n)
colors = cm.RdYlBu(np.linspace(0, 1, n))
pylab.bar(centers, arr['f0'], color=colors, align='center')
ax = pylab.gca()
ax.set_xticks(centers)
ax.set_xticklabels(arr['f1'], rotation=0)
pylab.show()
4 Comments
Eric O. Lebigot
I'm pretty sure that you can do this without having to handle the x-positioning (
sep, width, left, centers). In fact, you can simply use range(n) for set_xticks(), and use the align='center' parameter for bar().Eric O. Lebigot
Glad you found the remark useful. Here is another remark: it is easier to set
dtype=None in genfromtxt(): the data types are correctly inferred; you also get, as a free bonus, a bullet-proof code against fruit names that are longer than 20 characters. :)
unutbu
@EOL: Wow, I didn't know
dtype=None behaved different than omitting dtype. That's nice to know. Thanks again.Eric O. Lebigot
Yeah, this surprised me too, when I checked the docs. :) The default is
dtype=float (purely numerical arrays).As the others suggest, Matplotlib is your friend. Something like
import numpy as np
import matplotlib.pyplot as plt
plt.figure()
indices = np.arange(4)
width = 0.5
plt.bar(indices, [10, 3, 6, 10], width=width)
plt.xticks(indices + width/2, ('Apples', 'Oranges', 'Tomatoes', 'Pears'))
plt.show()
will get you started. Loading the data from a textfile is straight forward.
Comments
Felix is right.
Matplotlib is one of the tolls available. Take a look, it has lot of examples. If you're not able to draw a histogram then you could ask another question and I'm sure there will be lots of people to help.
Here are some examples:
http://matplotlib.sourceforge.net/examples/pylab_examples/histogram_demo_extended.html
