"""
Show how to modify the coordinate formatter to report the image "z"
value of the nearest pixel given x and y
"""
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.cm as cm

X = 10*np.random.rand(5, 3)

fig, ax = plt.subplots()
ax.imshow(X, interpolation='nearest')

numrows, numcols = X.shape


def format_coord(x, y):
    col = int(x + 0.5)
    row = int(y + 0.5)
    if col >= 0 and col < numcols and row >= 0 and row < numrows:
        z = X[row, col]
        return 'x=%1.4f, y=%1.4f, z=%1.4f' % (x, y, z)
    else:
        return 'x=%1.4f, y=%1.4f' % (x, y)

ax.format_coord = format_coord
plt.show()