AxLine

An infinitely long straight line can be added using ax.axline in a similar way as Matplotlib. This may be helpful, e.g., for adding an isoproportion line.

Note

Available with matplotlib>=3.3 and mpltern>=0.4.0

Unlike Matplotlib, slope is the displacement from the first argument and must be of length 3, whose sum should be zero. The sum of the first argument and slope is automatically scaled by ternary_sum.

With matplotlib>=3.4, a keyword argument transform can be given. Particularly when ax.transTernaryAxes is given, a line fixed to the triangle can be added by giving the first and the second arguments in the barycentric coordinates.

import matplotlib.pyplot as plt
import mpltern

ax = plt.subplot(projection="ternary")

ax.axline(
    [1.0, 0.0, 0.0],
    [0.0, 0.8, 0.2],
    color="C0",
)
ax.axline(
    [1.0, 0.0, 0.0],
    slope=[-0.2, 0.1, 0.1],
    color="C1",
)
ax.axline(
    [1.0, 0.0, 0.0],
    [0.0, 0.2, 0.8],
    color="C2",
    transform=ax.transTernaryAxes,
)

plt.show()