如何在matplotlib的第一个底部添加第二个x轴。

Question

我正在提到已经提出的问题here 在此示例中，用户通过将其添加到图表的上部与标题重合来解决第二轴问题。

问题： 是否可以在第一个x的底部添加第二个x轴？

代码：

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax1 = fig.add_subplot(111)
ax2 = ax1.twiny()

X = np.linspace(0,1,1000)
Y = np.cos(X*20)

ax1.plot(X,Y)
ax1.set_xlabel(r"Original x-axis: $X$")

new_tick_locations = np.array([.2, .5, .9])

def tick_function(X):
    V = 1/(1+X)
    return ["%.3f" % z for z in V]

ax2.set_xticks(new_tick_locations)
ax2.set_xticklabels(tick_function(new_tick_locations))
ax2.set_xlabel(r"Modified x-axis: $1/(1+X)$")
plt.show()

Answer 1

作为@DizietAsahi答案的替代方案，您可以使用与import numpy as np import matplotlib.pyplot as plt fig = plt.figure() ax1 = fig.add_subplot(111) ax2 = ax1.twiny() # Add some extra space for the second axis at the bottom fig.subplots_adjust(bottom=0.2) X = np.linspace(0,1,1000) Y = np.cos(X*20) ax1.plot(X,Y) ax1.set_xlabel(r"Original x-axis: $X$") new_tick_locations = np.array([.2, .5, .9]) def tick_function(X): V = 1/(1+X) return ["%.3f" % z for z in V] # Move twinned axis ticks and label from top to bottom ax2.xaxis.set_ticks_position("bottom") ax2.xaxis.set_label_position("bottom") # Offset the twin axis below the host ax2.spines["bottom"].set_position(("axes", -0.15)) # Turn on the frame for the twin axis, but then hide all # but the bottom spine ax2.set_frame_on(True) ax2.patch.set_visible(False) for sp in ax2.spines.itervalues(): sp.set_visible(False) ax2.spines["bottom"].set_visible(True) ax2.set_xticks(new_tick_locations) ax2.set_xticklabels(tick_function(new_tick_locations)) ax2.set_xlabel(r"Modified x-axis: $1/(1+X)$") plt.show() 发布的localhost示例类似的方式使用localhost。

ListActivity

here

Answer 2

我认为您必须创建第二个Axes，其高度为0（并隐藏yaxis）以获得第二个xaxis，您可以将其放置在任意位置。

例如：

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax1 = fig.add_axes((0.1,0.3,0.8,0.6)) # create an Axes with some room below

X = np.linspace(0,1,1000)
Y = np.cos(X*20)

ax1.plot(X,Y)
ax1.set_xlabel(r"Original x-axis: $X$")


# create second Axes. Note the 0.0 height
ax2 = fig.add_axes((0.1,0.1,0.8,0.0))
ax2.yaxis.set_visible(False) # hide the yaxis

new_tick_locations = np.array([.2, .5, .9])

def tick_function(X):
    V = 1/(1+X)
    return ["%.3f" % z for z in V]

ax2.set_xticks(new_tick_locations)
ax2.set_xticklabels(tick_function(new_tick_locations))
ax2.set_xlabel(r"Modified x-axis: $1/(1+X)$")
plt.show()