Position font relative to axis using ax.text, matplotlib

Question

I'm not sure how to properly position font relative to an axis object using matplotlib.

Example:

fig, axes = plt.subplots(nrows=1, ncols=3, figsize=(10, 4), dpi=100)
x = [1, 2]
y = [3, 4]

y_loc = 4.1
x_loc = 0.95
fs = 12
ax = axes[0]
ax.plot(x, y)
_ = ax.text(x=x_loc, y=y_loc, s="Plot 1", fontsize=fs)

ax = axes[1]
ax.plot(x, y)
_ = ax.text(x=x_loc, y=y_loc, s="Plot 2", fontsize=fs)

ax = axes[2]
_ = ax.plot(x, y)
_ = ax.text(x=x_loc, y=y_loc, s="Plot 3", fontsize=fs)

Which gives:

The use of values:

y_loc = 4.1
x_loc = 0.95

makes me think that there should be a better approach to this.

Note - I would like to use ax.text here, not title, and the question is mainly about how best to position text relative to a particular axis within a subplot. Ideally it would extend to a grid plot as well if it was just relative to a particular axis.

Answer 1

Default, ax.text uses "data coordinates", i.e. with x and y as shown on the ticks of the axes. To plot relative to the rectangle defined by the axes, use transform=ax.transAxes. Here 0,0 will be the point at the bottom left and 1,1 the point at the top right. (This kind of coordinates is also very useful when positioning a legend.)

from matplotlib import pyplot as plt
import numpy as np

fig, axes = plt.subplots(nrows=1, ncols=3, figsize=(10, 4), dpi=100)

for ind, ax in enumerate(axes):
    ax.plot(np.random.randint(0, 10, 2), np.random.randint(0, 10, 2))
    ax.text(x=0, y=1.05, s=f"Plot {ind+1}", fontsize=12, transform=ax.transAxes)
plt.show()