python - matplotlib 颜色条中的小刻度线

Question

我目前正在尝试在颜色栏中设置小刻度，但根本无法正常工作。我尝试了 3 种方法(请参阅下面的代码)，但它们似乎都不起作用。颜色条中是否真的可能有小刻度？

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import LogNorm
from matplotlib.ticker import FixedLocator, FormatStrFormatter

# fill grid
x = np.linspace(1,10,10)
y = np.linspace(1,10,10)

X, Y = np.meshgrid(x,y)
Z = np.abs(np.cos(X**2 - Y**2) * X**2 * Y)

# plot
f, ax = subplots(1)
p = plt.pcolormesh(X, Y, Z, norm=LogNorm(), vmin=1e-2, vmax=1e2)
cb = plt.colorbar(p, ax=ax, orientation='horizontal', aspect=10)

minor_ticks = np.arange(1,10,2)
#cb.set_ticks(minor_ticks, minor=True) # error: doesn't support keyword argument 'minor'
#cb.ax.xaxis.set_ticks(minor_ticks, minor=True) # plots an extremely small colorbar, with wrong ticks
#cb.ax.xaxis.set_minor_locator(FixedLocator(minor_ticks)) # nothing happens
plt.show()

Answer 1

您走在正确的轨道上，您只需要 cb.ax.minorticks_on()。

例如:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import LogNorm

# fill grid
x = np.linspace(1,10,10)
y = np.linspace(1,10,10)

X, Y = np.meshgrid(x,y)
Z = np.abs(np.cos(X**2 - Y**2) * X**2 * Y)

# plot
f, ax = plt.subplots()
p = plt.pcolormesh(X, Y, Z, norm=LogNorm(), vmin=1e-2, vmax=1e2)
cb = plt.colorbar(p, ax=ax, orientation='horizontal', aspect=10)

cb.ax.minorticks_on()

plt.show()

---

如果您只需要您指定的刻度，您仍然以“正常”方式设置它们，但请注意，无论数据范围如何，颜色条轴坐标系的范围都是 0-1。

因此，要设置您想要的特定值，我们需要使用图像正在使用的相同 norm 实例调用标准化刻度位置。

例如:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import LogNorm

# fill grid
x = np.linspace(1,10,10)
y = np.linspace(1,10,10)

X, Y = np.meshgrid(x,y)
Z = np.abs(np.cos(X**2 - Y**2) * X**2 * Y)

# plot
f, ax = plt.subplots()
p = plt.pcolormesh(X, Y, Z, norm=LogNorm(), vmin=1e-2, vmax=1e2)
cb = plt.colorbar(p, ax=ax, orientation='horizontal', aspect=10)

# We need to nomalize the tick locations so that they're in the range from 0-1...
minorticks = p.norm(np.arange(1, 10, 2))
cb.ax.xaxis.set_ticks(minorticks, minor=True)

plt.show()