如何在 matplotlib 中扩展线性回归图

Question

我在尝试将绘图的直线部分拟合为线性部分时遇到了问题。为了完成我的绘图，我必须延长红线，就好像它是一条直线一样，以便可以观察到它与至少 x 轴的交点。

我的代码是：

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

#data = pd.read_csv("LPPII_cw_2_1.csv")

#f = data["f [kHz]"] 
f = (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500)

#h21e = data["h21e [A/A]"]
h21e = (218., 215., 210., 200., 189., 175., 165., 150., 140., 129., 120., 69., 30.)

linearf = f[-3:]
linearh = h21e[-3:]

logA = np.log(linearf)
logB = np.log(linearh)

m, c = np.polyfit(logA, logB, 1, w=np.sqrt(linearh))
y_fit = np.exp(m*logA + c)

fig, ax = plt.subplots()

ax.set_xscale('log')
ax.set_yscale('log')

ax.set_xlabel('f [kHz]')
ax.set_ylabel('h$_{21e}$ [A/A]')

ax.scatter(f, h21e, marker='.', color='k')
ax.plot(linearf, y_fit, color='r', linestyle='-')

plt.show()

我的情节是这样的：

Answer 1

您可以添加 x 轴的最大值并将其附加在 linearf 的末尾。然后计算曲线，并画出它。需要保存并重置旧的 y 限制，以防止 matplotlib 自动扩展这些限制。请注意，只有在绘制散点图后才能提取 x-lims。

import matplotlib.pyplot as plt
import numpy as np

f = (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 500)
h21e = (218., 215., 210., 200., 189., 175., 165., 150., 140., 129., 120., 69., 30.)

linearf = f[-3:]
linearh = h21e[-3:]

logA = np.log(linearf)
logB = np.log(linearh)

m, c = np.polyfit(logA, logB, 1, w=np.sqrt(linearh))

fig, ax = plt.subplots()

ax.set_xscale('log')
ax.set_yscale('log')

ax.set_xlabel('f [kHz]')
ax.set_ylabel('h$_{21e}$ [A/A]')

ax.scatter(f, h21e, marker='.', color='k')

linearf_ext = list(linearf) + [ax.get_xlim()[1]]
logA = np.log(linearf_ext)
y_fit = np.exp(m * logA + c)
ymin, ymax = ax.get_ylim()
ax.plot(linearf_ext, y_fit, color='r', linestyle='-')
ax.set_ylim(ymin, ymax)
plt.tight_layout()
plt.show()

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