Aspect

The triangle aspect can be modified by ax.set_aspect. For more general triangles, use rotation and/or corners.

import matplotlib.pyplot as plt
from mpltern.datasets import get_spiral


ax = plt.subplot(projection='ternary')
ax.plot(*get_spiral())

ax.set_aspect(1.5)

ax.set_tlabel('Top')
ax.set_llabel('Left')
ax.set_rlabel('Right')

plt.show()