29

Annoying strange problem and I have not been able to find a solution on this site yet (although the question has popped up)

I am trying to make a histogram where the bins have the 'bar style' where vertical lines separate each bin but no matter what I change the histtype constructor to I get a step filled histogram.

Here is my code. Note I am using jupyter notebook installed via anaconda with python version 2.7.6

import numpy as np
import matplotlib.pyplot as plt

x = np.random.rand((100)) 
bins = np.linspace(0, 2, 40)
plt.title('Relative Amplitude',fontsize=30)
plt.xlabel('Random Histogram')
plt.ylabel('Frequency',fontsize=30)
plt.hist(x, bins, alpha=0.5, histtype='bar')

plt.legend(loc='upper right',fontsize=30)
plt.xticks(fontsize = 20) 
plt.yticks(fontsize = 20) 
plt.show()

Thats it and I get a step filled diagram with no vertical lines separating the bars. What is annoying is that I didn't have this problem awhile ago, something clearly has changed and I don't know what.I have tried histype='barstacked' as well. Thank you kindly for your help

enter image description here

Canuck
  • 567
  • 1
  • 7
  • 15

3 Answers3

66

Using your example:

import numpy as np
import matplotlib.pyplot as plt

x = np.random.rand((100)) 
bins = np.linspace(0, 2, 40)
plt.title('Relative Amplitude',fontsize=30)
plt.xlabel('Random Histogram')
plt.ylabel('Frequency',fontsize=30)
plt.hist(x, bins, alpha=0.5, histtype='bar', ec='black')

plt.legend(loc='upper right',fontsize=30)
plt.xticks(fontsize = 20) 
plt.yticks(fontsize = 20) 
plt.show()

Which produces the following image:

enter image description here

The key difference is the use of the ec keyword argument. This is shorthand for edgecolor and using it has the same effect as edgecolor.

In the documentation for plt.hist it says that in addition to all of the listed keyword arguments, plt.hist also takes keyword arguments for the Patch initializer. edgecolor (and ec) is one of those keyword arguments. That's why it's not explicitly listed in the documentation for plt.hist. All of the bars in the plot are an individual Patch object, so you're saying you want all of the bars to be drawn with a black outline (or edgecolor in matplotlib jargon).

ngoldbaum
  • 5,430
  • 3
  • 28
  • 35
  • 1
    Thanks Nathan! I am still unsure as to why I need to add that command now and before there was no need but if it works it works... – Canuck Mar 01 '17 at 21:49
  • 4
    The key difference is the use of the `ec` keyword argument. This is short of `edgecolor`. In the documentation for `plt.hist` it says that in addition to all of the listed keyword arguments, `plt.hist` *also* takes keyword arguments for the `Patch` initializer. `edgecolor` is one of those keyword arguments. That's why it's not explicitly listed in the documentation for `plt.hist`. All of the bars in the plot are an individual `Patch` object, so you're saying you want all of the bars to be drawn with a black outline (or `edgecolor` in matplotlib jargon). – ngoldbaum Mar 01 '17 at 21:56
  • 1
    @ngoldbaum Adding your comment into your answer would be very helpful, as your answer itself requires careful comparison to the OP's question in order to figure out what you did differently. Thanks! – spacetyper Aug 21 '18 at 18:44
2

It works for me if I give different colors to the edgecolor argument and the color argument. For example:

import numpy as np
import matplotlib.pyplot as plt

x = np.random.rand((100)) 
bins = np.linspace(0, 2, 40)
plt.title('Relative Amplitude',fontsize=30)
plt.xlabel('Random Histogram')
plt.ylabel('Frequency',fontsize=30)
plt.hist(x, bins, alpha=0.5,edgecolor='black',color='steelblue', histtype='bar')

plt.legend(loc='upper right',fontsize=30)
plt.xticks(fontsize = 20) 
plt.yticks(fontsize = 20) 
plt.show()
Krishna Totewad
  • 21
  • 1
0

You can use rwidth Parameter in plt.hist. Note I am using matplotlib version '3.4.2'.

rwidth : float or None, default: None The relative width of the bars as a fraction of the bin width. If None, automatically compute the width.

import numpy as np
import matplotlib.pyplot as plt

x = np.random.rand((100)) 
bins = np.linspace(0, 2, 40)
plt.title('Relative Amplitude',fontsize=30)
plt.xlabel('Random Histogram', fontsize=30)
plt.ylabel('Frequency',fontsize=30)
plt.hist(x, bins, rwidth=0.6, alpha=0.5, histtype='bar')# rwidth specify the width of the bars
# rwidth is an number between 0 and 1

plt.xticks(fontsize=15) 
plt.yticks(fontsize=15)
plt.xlim(0,1)
plt.show()

Which product this image(click here)

Qavi
  • 36
  • 3