Python matplotlib 如何更改“直方图”的 y 值

Question

I am trying to create a "histogram", except the y-axis is not supposed to be the frequency of data points within a bin. Instead, I wish to set my own y-axis values for each bin.

For example, let's say my x values are: [1, 2.2, 1.4, 2, 3.3, 2.6, 3, 1.5, 3.9] and my y-values are [1, 2, 2.5, 1, 0.5, 3, 4, 3, 2]

Treat this as a function: each of the x values corresponds to the y -values (ie, the value in the 1st index of x array maps to the value in the 1st index of y array, 2nd index to 2nd, etc.).

I wish to bin the x values and plot the sum of the y values corresponding to the x values of each bin.

For example, let's say I were to create 3 bins. The first bin would contain the x values 1, 1.4, 1.5, and what gets plotted for this bin is the sum of the corresponding y values (so 1 + 2.5 + 3 = 6.5 ).

How can I achieve this?

Edit: I guess a simpler question is: how do I create a bar graph with numerical numbers as the x-axis and with continuous bars (ie no gap between bars)

Answer 1

I used your example data, and here is the code

import numpy as np

x = np.array([1, 2.2, 1.4, 2, 3.3, 2.6, 3, 1.5, 3.9])
# sort x and y
ind = np.argsort(x)
x1 = x[ind]
y = np.array([1, 2, 2.5, 1, 0.5, 3, 4, 3, 2])
y1 = y[ind]

# count bins
y2, t = np.histogram(x1, bins=3)
ind1 = y2.cumsum()
ind2 = np.array([0]+[e for e in ind1[0:-1]])

# sum based on counts
y_final = [y1[i:j].sum() for (i, j) in zip(ind2, ind1)]

# plot bar, specify the width
fig, ax = plt.subplots(1, 1, figsize=(7.2, 7.2))
ax.bar(t[0:3], y_final, width=np.diff(t)[0])

Answer 2

You seem to be describing the weights= argument of plt.hist :

import matplotlib.pyplot as plt

x = [1, 2.2, 1.4, 2, 3.3, 2.6, 3, 1.5, 3.9]
y = [1, 2, 2.5, 1, 0.5, 3, 4, 3, 2]
plt.hist(x, weights=y, bins=3)

At the left the default histogram and at the center with histtype='step' which more resembles how a function would be plotted. The subplot at the right adds a stem plot showing the x and corresponding y values.