在pandas/matplotlib中获取散点图的Colorbar实例

Question

如何获取由pandas.DataFrame.plot创建的绘图的内部创建的colorbar实例？

以下是生成彩色散点图的示例:

import matplotlib.pyplot as plt
import pandas as pd
import numpy as np
import itertools as it

# [ (0,0), (0,1), ..., (9,9) ]
xy_positions = list( it.product( range(10), range(10) ) )

df = pd.DataFrame( xy_positions, columns=['x','y'] )

# draw 100 floats
df['score'] = np.random.random( 100 )

ax = df.plot( kind='scatter',
              x='x',
              y='y',
              c='score',
              s=500)
ax.set_xlim( [-0.5,9.5] )
ax.set_ylim( [-0.5,9.5] )

plt.show()

这给了我一个像这样的数字:

如何获取colorbar实例以便操作它,例如更改标签或设置刻度？

Answer 1

pandas 不返回颜色条的轴,因此我们必须找到它:

1,让我们得到figure实例:即使用plt.gcf()

In [61]:

import matplotlib.pyplot as plt
import pandas as pd
import numpy as np
import itertools as it

# [ (0,0), (0,1), ..., (9,9) ]
xy_positions = list( it.product( range(10), range(10) ) )

df = pd.DataFrame( xy_positions, columns=['x','y'] )

# draw 100 floats
df['score'] = np.random.random( 100 )

ax = df.plot( kind='scatter',
              x='x',
              y='y',
              c='score',
              s=500)
ax.set_xlim( [-0.5,9.5] )
ax.set_ylim( [-0.5,9.5] )

f = plt.gcf()

2,这个数字有多少轴？

In [62]:

f.get_axes()
Out[62]:
[<matplotlib.axes._subplots.AxesSubplot at 0x120a4d450>,
 <matplotlib.axes._subplots.AxesSubplot at 0x120ad0050>]

3,第一个轴(即创建的第一个轴)包含图

In [63]:

ax
Out[63]:
<matplotlib.axes._subplots.AxesSubplot at 0x120a4d450>

4,因此,第二轴是彩条轴

In [64]:

cax = f.get_axes()[1]
#and we can modify it, i.e.:
cax.set_ylabel('test')