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python matplotlib plot curve

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Accepted Answer
March 24, 2026 Score: 4 Rep: 507 Quality: High Completeness: 80%

You can simple change plt.xscale('symlog') to plt.xscale('log'). 'symlog' is an extension of the 'log' scale for negative values, which you do not need here. Naturally, this extension is not seamless, and it needs to remove values under a small threshhold. That is what is causing you issues here.

Figure without artefacts

Be careful if you need to plot for values starting at 0.1, you need to change t at the begining.

Full code:

import numpy as np
import matplotlib.pyplot as plt
t = np.logspace(-1, 4, 100)
CP = 400
Pan = 1100
tau = 30
P = CP+Pan/(1+t/tau)
dPdPan = 1/(1+t/tau)
dPdtau = (Pan*t)/(tau2*(1+t/tau)2)
SCP = CP/P
normpan = (dPdPan - dPdPan.min()) / (dPdPan.max() - dPdPan.min())
normtau = (dPdtau - dPdtau.min()) / (dPdtau.max() - dPdtau.min())
plt.figure(figsize=(6,4))
plt.plot(t, normpan, label=r'$\text{P}\text{an}$')
plt.plot(t, normtau, label=r'$\tau$')
plt.plot(t, SCP, label="CP")
plt.vlines(tau, 0, max(normtau), linestyles=':', colors="dimgray", alpha=.4, lw=1.5)
plt.xscale('log')
plt.xlim(0.1, 10001)
plt.ylim(0, 1.05)
ax = plt.gca()
ax.spines["top"].setvisible(False)
ax.spines["right"].setvisible(False)
ax.setxticks([1, 10, tau, 100, 1000, 10000])
ax.setxticklabels([1, 10, r'$\tau$', 100, 1000, 10000])
plt.legend(fontsize=9, frameon=False, loc='center right')
plt.tightlayout()
plt.show()