Question

使用maptplotlib，我使用scatter方法绘制一些点（参见下面的代码）。我想单独标记每个点。

此代码会使用labels数组标记每个点，但我希望我的第一个点标有labels[0]，第二个点标有labels[1]，依此类推。

import numpy as np; import matplotlib.pyplot as plt
y = np.arange(10) # points to plot
labels = np.arange(10) # labels of the points
fig, ax = plt.subplots(nrows=1, ncols=1)
ax.scatter(x=np.arange(10), y=y, label=labels, picker=3)

有没有办法做到这一点？顺便说一句，有没有办法迭代ax中的点？方法ax.get_children()产生我不理解的数据。

谢谢！

Answer 1

假设您没有绘制多个散点，您可以为每个点做scatter：

import numpy as np; import matplotlib.pyplot as plt
y = np.arange(10) # points to plot
x=np.arange(10)
labels = np.arange(10) # labels of the points
fig, ax = plt.subplots(nrows=1, ncols=1)
for x_,y_,label in zip(x,y,labels):
    ax.scatter([x_], [y_], label=label, picker=3)

如果您正在绘制数千或数万个点，这将开始滞后，但如果只是少数几个点，则没有问题。

要回答问题的第二部分，ax.get_children()会返回组成这些轴的对象列表，例如：

[<matplotlib.axis.XAxis at 0x103acc410>,
 <matplotlib.axis.YAxis at 0x103acddd0>,
 <matplotlib.collections.PathCollection at 0x10308ba10>, #<--- this is a set of scatter points
 <matplotlib.text.Text at 0x103082d50>,
 <matplotlib.patches.Rectangle at 0x103082dd0>,
 <matplotlib.spines.Spine at 0x103acc2d0>,
 <matplotlib.spines.Spine at 0x103ac9f90>,
 <matplotlib.spines.Spine at 0x103acc150>,
 <matplotlib.spines.Spine at 0x103ac9dd0>]

如果您只想在轴上获取散点图集，最简单的方法是ax.collections。这是list，其中包含在轴上绘制的所有collections个实例（散点属于PathCollection）。

In [9]: ax.collections
Out[9]: [<matplotlib.collections.PathCollection at 0x10308ba10>]

如果您为每个点绘制了单独的scatter，则迭代这些点非常简单：

# iterate over points and turn them all red
for point in ax.collections:
    point.set_facecolor("red")

Answer 2

所有这些都可以隐藏在函数或类中：

# import stuff
import matplotlib.pyplot as plt
import numpy as np

# create dictionary we will close over (twice)
label_dict = dict()
# helper function to do the scatter plot + shove data into label_dict
def lab_scatter(ax, x, y, label_list, *args, **kwargs):
    if 'picker' not in kwargs:
        kwargs['picker'] = 3
    sc = ax.scatter(x, y, *args, **kwargs)
    label_dict[sc] = label_list
    return sc
# call back function which also closes over label_dict, should add more sanity checks
# (that artist is actually in the dict, deal with multiple hits in ind ect)
def cb_fun(event):
    # grab list of labels from the dict, print the right one
    print label_dict[event.artist][event.ind[0]]
# create the figure and axes to use
fig, ax = plt.subplots(1, 1)
# loop over 5 synthetic data sets
for j in range(5):
    # use our helper function to do the plotting
    lab_scatter(ax,
                np.ones(10) * j,
                np.random.rand(10),
                # give each point a unique label
                label_list = ['label_{s}_{f}'.format(s=j, f=k) for k in range(10)])
# connect up the call back function
cid = fig.canvas.mpl_connect('pick_event', cb_fun)

Matplotlib：如何单独标记点？

2 个答案: