I am using IPython Notebook to view matplotlib graphs. I have noticed many times that the markers are drawn slightly off-center. Here is an example:

Closeup:

Code to reproduce:

%matplotlib inline
import numpy as np
import matplotlib.pyplot as plt

t = np.linspace(-1,1,40)
plt.plot(t,t**3 - 0.75*t,'.-',linewidth=0.3)
plt.grid(True)

Matplotlib version

• Operating system: Windows 10
• Matplotlib version: 2.2.2'
• Matplotlib backend (print(matplotlib.get_backend())): module://ipykernel.pylab.backend_inline
• Python version: 2.7.15 from Anaconda Python
• Jupyter version (if applicable): 5.5.0
• Other libraries: n/a