Set string values on matplotlib x axis

Question

Using below code I'm attempting to plot x axis values as strings with matplotlib :

import matplotlib.pyplot as plt
import pandas as pd
import numpy as np

fig = plt.figure()
plt.figure(figsize=(20,10))
plt.xticks(fontsize=24)
plt.yticks(fontsize=24)

plt.plot( 'x', 'y', data=pd.DataFrame({'x': np.array(['a' , 'b' , 'c']) , 'y': np.array([1,2,3]) }), marker=None, color='blue')


plt.show()

This error is returned :

ValueError: could not convert string to float: 'c'

It appears matplotlib is inferring the axis value as string. How to change this ?

I've tried setting the type but this does not fix :

astype(str)

No errors here either, python 2 or 3. Could you describe in more detail what you want the plot to look like? And also provide more of the stack trace -- is it plt.plot() that returns the error? — Bonlenfum
– Bonlenfum, Commented Oct 26, 2018 at 9:17

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

I can reproduce the error in python2 with matplotlib==1.5.3.

If you are using python3

Upgrading matplotlib to newest can solve this problem:

pip3 install matplotlib --upgrade

If you are using python2

Because the newest matplotlib doesn't support 2.x, you can upgrade to matplotlib==2.1:

pip2 install matplotlib==2.1

If you don't want to upgrade

Try this:

import matplotlib.pyplot as plt
import pandas as pd
import numpy as np

plt.figure(figsize=(20,10))
plt.yticks(fontsize=24)
x = np.array(['a' , 'b' , 'c'])
xn = range(len(x))
plt.xticks(xn, x, fontsize=24)

plt.plot(xn, 'y', data=pd.DataFrame({'y': np.array([1,2,3]) }), marker=None, color='blue')
plt.show()

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Oct 26, 2018 at 9:27

Hao Li

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Set string values on matplotlib x axis

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