Plotting an array in histogram style without using hist function in Python with Matplotlib

Question

How do i plot an array in a histogram style using matplotlib.plot() or similar functions?

I also use scikit as a package but im completely new to that one and have not found an alternative there either so far.

The function hist in matplotlib calculates the histogram (e.g. of a picture) and plots it. However, for my assignment i have to calculate the histogram myself as an array of shape (256,), where each index corresponds to a calculated grey-scale value from 0 to 255.

So far i looked at the different parameters of matplotlib.plot() but could not see or figure out a way to plot in a hist style.

I am sure you can calculate your histogram with the keywords provided by matplotlib hist, e.g., the bin parameter. — Mr. T
– Mr. T, Commented Mar 30, 2022 at 21:42
@Mr.T the bins parameter lets you choose your resolution. If you set it to 256 in my case, you will get a bin for each value, reduce it to 128 and 2 bins will be merged together reducing resolution. However, i still would like to use my own calculated array, which i cant when i use hist. Using my array with hist would yield me a histogram of my histogram. — Max Schmidt
– Max Schmidt, Commented Mar 30, 2022 at 21:48
bins: int or sequence or str - it takes an array, if that is what you want. — Mr. T
– Mr. T, Commented Mar 30, 2022 at 21:51

Helmut · Accepted Answer · 2022-03-30 21:52:54Z

1

Try calculating the histogram and than plotting this as bars?

import numpy as np
from matplotlib import pyplot as plt

dummie_data = np.random.randint(0, 256, (100,100))

values, count = np.unique(dummie_data, return_counts=True)

plt.figure(figsize=(10,6))
plt.bar(values, count/dummie_data.size, width=1)
plt.show()

By using:

plt.bar(values, count, width=1)

You use the absolute frequency.

answered Mar 30, 2022 at 21:52

Helmut

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Max Schmidt Over a year ago

Thank you very much, thats exactly what i needed.

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