将鼠标悬停在matplotlib中的某个点上时，是否可以使标签出现? [英] Is it possible to make labels appear when hovering mouse over a point in matplotlib?

问题描述

我正在使用 matplotlib 制作散点图.散点图上的每个点都与一个命名对象相关联.当我将光标悬停在与该对象关联的散点图上的点上时，我希望能够看到该对象的名称.特别是，能够快速查看异常值点的名称会很好.我在此处搜索时能够找到的最接近的东西是注释命令，但这似乎在绘图上创建了固定标签.不幸的是，根据我拥有的点数，如果我标记每个点，则散点图将无法读取.有谁知道一种创建仅在光标悬停在该点附近时才会显示的标签的方法吗?

I am using matplotlib to make scatter plots. Each point on the scatter plot is associated with a named object. I would like to be able to see the name of an object when I hover my cursor over the point on the scatter plot associated with that object. In particular, it would be nice to be able to quickly see the names of the points that are outliers. The closest thing I have been able to find while searching here is the annotate command, but that appears to create a fixed label on the plot. Unfortunately, with the number of points that I have, the scatter plot would be unreadable if I labeled each point. Does anyone know of a way to create labels that only appear when the cursor hovers in the vicinity of that point?

推荐答案

似乎这里没有其他答案可以真正回答这个问题.所以这里的代码使用散点并在悬停在散点上时显示注释.

It seems none of the other answers here actually answer the question. So here is a code that uses a scatter and shows an annotation upon hovering over the scatter points.

import matplotlib.pyplot as plt
import numpy as np; np.random.seed(1)

x = np.random.rand(15)
y = np.random.rand(15)
names = np.array(list("ABCDEFGHIJKLMNO"))
c = np.random.randint(1,5,size=15)

norm = plt.Normalize(1,4)
cmap = plt.cm.RdYlGn

fig,ax = plt.subplots()
sc = plt.scatter(x,y,c=c, s=100, cmap=cmap, norm=norm)

annot = ax.annotate("", xy=(0,0), xytext=(20,20),textcoords="offset points",
                    bbox=dict(boxstyle="round", fc="w"),
                    arrowprops=dict(arrowstyle="->"))
annot.set_visible(False)

def update_annot(ind):

    pos = sc.get_offsets()[ind["ind"][0]]
    annot.xy = pos
    text = "{}, {}".format(" ".join(list(map(str,ind["ind"]))), 
                           " ".join([names[n] for n in ind["ind"]]))
    annot.set_text(text)
    annot.get_bbox_patch().set_facecolor(cmap(norm(c[ind["ind"][0]])))
    annot.get_bbox_patch().set_alpha(0.4)


def hover(event):
    vis = annot.get_visible()
    if event.inaxes == ax:
        cont, ind = sc.contains(event)
        if cont:
            update_annot(ind)
            annot.set_visible(True)
            fig.canvas.draw_idle()
        else:
            if vis:
                annot.set_visible(False)
                fig.canvas.draw_idle()

fig.canvas.mpl_connect("motion_notify_event", hover)

plt.show()

因为人们还希望将此解决方案用于线 plot 而不是散点图，以下是 plot 的相同解决方案(工作方式略有不同).

Because people also want to use this solution for a line plot instead of a scatter, the following would be the same solution for plot (which works slightly differently).

import matplotlib.pyplot as plt
import numpy as np; np.random.seed(1)

x = np.sort(np.random.rand(15))
y = np.sort(np.random.rand(15))
names = np.array(list("ABCDEFGHIJKLMNO"))

norm = plt.Normalize(1,4)
cmap = plt.cm.RdYlGn

fig,ax = plt.subplots()
line, = plt.plot(x,y, marker="o")

annot = ax.annotate("", xy=(0,0), xytext=(-20,20),textcoords="offset points",
                    bbox=dict(boxstyle="round", fc="w"),
                    arrowprops=dict(arrowstyle="->"))
annot.set_visible(False)

def update_annot(ind):
    x,y = line.get_data()
    annot.xy = (x[ind["ind"][0]], y[ind["ind"][0]])
    text = "{}, {}".format(" ".join(list(map(str,ind["ind"]))), 
                           " ".join([names[n] for n in ind["ind"]]))
    annot.set_text(text)
    annot.get_bbox_patch().set_alpha(0.4)


def hover(event):
    vis = annot.get_visible()
    if event.inaxes == ax:
        cont, ind = line.contains(event)
        if cont:
            update_annot(ind)
            annot.set_visible(True)
            fig.canvas.draw_idle()
        else:
            if vis:
                annot.set_visible(False)
                fig.canvas.draw_idle()

fig.canvas.mpl_connect("motion_notify_event", hover)

plt.show()

如果有人正在寻找双轴直线的解决方案，请参阅 如何使鼠标悬停在多轴上的一个点上时出现标签?

In case someone is looking for a solution for lines in twin axes, refer to How to make labels appear when hovering over a point in multiple axis?

如果有人正在寻找条形图的解决方案，请参阅例如这个答案.

In case someone is looking for a solution for bar plots, please refer to e.g. this answer.

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