Python Barplot ValueError: could not convert string to float:

Question

I try to plot a simple barplot in Python, but when I run the code:

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
x=['A','B','C','D','E','F','G','H','I','J']
y=[47, 23, 27,  0, 82,  7, 46, 92, 36, 76]
plt.bar(x,y)
plt.xlabel('Categories')
plt.ylabel("Values")
plt.title('Categories Bar Plot')
plt.show()

I get an error message:

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

I don't know why this does not work, especially because it's an exact copy of an example from a website which should work.

This works fine with the current version of matplotlib. I'm voting to close this as not reproducible. — Trenton McKinney
– Trenton McKinney, Commented Nov 10, 2021 at 14:30

mozway · Accepted Answer · 2021-11-10 10:54:03Z

2

Which pandas/matplotlib versions are you using? Have you made sure to use a clean environment?

You code works fine for me.

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
x=['A','B','C','D','E','F','G','H','I','J']
y=[47, 23, 27,  0, 82,  7, 46, 92, 36, 76]
plt.bar(x,y)
plt.xlabel('Categories')
plt.ylabel("Values")
plt.title('Categories Bar Plot')
plt.show()

output:

answered Nov 10, 2021 at 10:54

mozway

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4 Comments

palatinepython Over a year ago

OK thanks a lot, I will try to shut down and restart everything

mozway Over a year ago

the error is quite strange since "plotting" letters should work (try plt.bar(x,x)), thus my question on matplotlib's version

palatinepython Over a year ago

It was because I have to use matplotlib 1.5.1, down under I posted my workaround

mozway Over a year ago

Thanks for providing a feedback to the community ;)

palatinepython · Accepted Answer · 2021-11-10 12:09:07Z

Turns out, I use matplotlib 1.5.1 and I can't upgrade it because of reasons I can't write here. But I wrote a workaround I wanted to share with the community:

x1=['A','B','C','D','E','F','G','H','I','J']
N=0
x2=[]
for i in range(len(x1)):
    x2.append(N)
    N+=1
y=[47, 23, 27,  0, 82,  7, 46, 92, 36, 76]
plt.bar(x2,y)
plt.xlabel('Categories')
plt.ylabel("Values")
plt.title('Categories Bar Plot')
plt.xticks(np.arange(0.5, len(x2)+0.5), list(x1), rotation=90, size = '10')
plt.show()

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