matplotlib strings as labels on x axis

Question

I am building a small tool for data analysis and I have come to the point, where I have to plot the prepared data. The code before this produces the following two lists with equal length.

t11 = ['00', '01', '02', '03', '04', '05', '10', '11', '12', '13', '14', '15', '20', '21', '22', '23', '24', '25', '30', '31', '32', '33', '34', '35', '40', '41', '42', '43', '44', '45', '50', '51', '52', '53', '54', '55']

t12 = [173, 135, 141, 148, 140, 149, 152, 178, 135, 96, 109, 164, 137, 152, 172, 149, 93, 78, 116, 81, 149, 202, 172, 99, 134, 85, 104, 172, 177, 150, 130, 131, 111, 99, 143, 194]

Based on this, I want to built a histogram with matplotlib.plt.hist. However, there are a couple of problems: 1. t11[x] and t12[x] are connected for all x. Where t11[x] is actually a string. It represents a certain detector combination. For example: '01' tells that the detection was made in the 0th segment of the first detector, and 1st segment of the second detector. My goal is to have each entry from t11 as a labeled point on the x axis. The t12 entry is going to define the hight of the bar above the t11 entry (on a logarithmic y axis)

How does one configure such an x axis? 2. This is all very new to me. I could not find anything related in the documentation. Most probably because I did not know what to search for. SO: Is there an "official" name for what I am trying to achieve. This would also help me alot.

David Jones · Accepted Answer · 2019-04-03 09:37:27Z

81

Use the xticks command.

import matplotlib.pyplot as plt

t11 = ['00', '01', '02', '03', '04', '05', '10', '11', '12', '13', '14', '15',
       '20', '21', '22', '23', '24', '25', '30', '31', '32', '33', '34', '35',
       '40', '41', '42', '43', '44', '45', '50', '51', '52', '53', '54', '55']

t12 = [173, 135, 141, 148, 140, 149, 152, 178, 135, 96, 109, 164, 137, 152,
       172, 149, 93, 78, 116, 81, 149, 202, 172, 99, 134, 85, 104, 172, 177,
       150, 130, 131, 111, 99, 143, 194]


plt.bar(range(len(t12)), t12, align='center')
plt.xticks(range(len(t11)), t11, size='small')
plt.show()

edited Apr 3, 2019 at 9:37

David Jones

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answered Sep 26, 2011 at 18:47

Stephen Terry

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3 Comments

User Over a year ago

Why'd you use len(t12) in both lines? Shouldn't one be len(t11)?

hoffee Over a year ago

@User Generally yes, you're right. When calling xticks you typically want the number of ticks to be equal to the number of labels. In this case though the length of both lists is the same so it doesn't really matter.

luator Over a year ago

bar has an argument tick_label which can be used instead of plt.xticks, i.e. plt.bar(..., tick_label=t11).

Tereso del Río Almajano · Accepted Answer · 2022-05-10 12:25:45Z

53

For the object oriented API of matplotlib one can plot custom text on the x-ticks of an axis with following code:

x = np.arange(2,10,2)
y = x.copy()
x_ticks_labels = ['jan','feb','mar','apr']

fig, ax = plt.subplots(1,1) 
ax.plot(x,y)

# Set number of ticks for x-axis
ax.set_xticks(x)
# Set ticks labels for x-axis
ax.set_xticklabels(x_ticks_labels, rotation='vertical', fontsize=18)

edited May 10, 2022 at 12:25

Tereso del Río Almajano

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answered Apr 17, 2017 at 21:46

David Alvarez

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Comments

Community · Accepted Answer · 2017-05-23 12:17:55Z

3

In matplotlib lingo, you are looking for a way to set custom ticks.

It seems you cannot achieve this with the pyplot.hist shortcut. You will need to build your image step by step instead. There is already an answer here on Stack Overflow to question which is very similar to yours and should get you started: Matplotlib - label each bin

edited May 23, 2017 at 12:17

CommunityBot

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answered Sep 26, 2011 at 18:45

Ludovico Fischer

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Comments

Colin Dickie · Accepted Answer · 2017-11-16 18:36:00Z

3

Firstly you need to access the axis object:

fig, ax = plt.subplots(1,1)

then:

ax.set_yticks([x for x in range(-10,11)])
ax.set_yticklabels( ['{0:2d}'.format(abs(x)) for x in range(-10, 11)])

answered Nov 16, 2017 at 18:36

Colin Dickie

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