Question

我正使用seaborn绘制多个数据帧作为点图。此外，我正在绘制同一轴上的所有数据框。

如何在情节中添加图例？

我的代码获取每个数据框并在同一图上一个接一个地绘制它。

每个数据框都有相同的列

date        count
2017-01-01  35
2017-01-02  43
2017-01-03  12
2017-01-04  27

我的代码：

f, ax = plt.subplots(1, 1, figsize=figsize)
x_col='date'
y_col = 'count'
sns.pointplot(ax=ax,x=x_col,y=y_col,data=df_1,color='blue')
sns.pointplot(ax=ax,x=x_col,y=y_col,data=df_2,color='green')
sns.pointplot(ax=ax,x=x_col,y=y_col,data=df_3,color='red')

这在同一图上绘制了3条线。然而传说却缺失了。 The documentation不接受label参数。

一种有效的解决方法是创建新的数据框并使用hue argument。

df_1['region'] = 'A'
df_2['region'] = 'B'
df_3['region'] = 'C'
df = pd.concat([df_1,df_2,df_3])
sns.pointplot(ax=ax,x=x_col,y=y_col,data=df,hue='region')

但我想知道是否有一种方法可以为代码创建一个图例，该图例首先将点图连续添加到图中，然后添加图例。

示例输出：

Answer 1

我建议不要使用seaborn pointplot进行绘图。这使事情变得不必要地复杂化而是使用matplotlib plot_date。这允许为图表设置标签，并使用ax.legend()自动将它们放入图例中。

import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns
import numpy as np

date = pd.date_range("2017-03", freq="M", periods=15)
count = np.random.rand(15,4)
df1 = pd.DataFrame({"date":date, "count" : count[:,0]})
df2 = pd.DataFrame({"date":date, "count" : count[:,1]+0.7})
df3 = pd.DataFrame({"date":date, "count" : count[:,2]+2})

f, ax = plt.subplots(1, 1)
x_col='date'
y_col = 'count'

ax.plot_date(df1.date, df1["count"], color="blue", label="A", linestyle="-")
ax.plot_date(df2.date, df2["count"], color="red", label="B", linestyle="-")
ax.plot_date(df3.date, df3["count"], color="green", label="C", linestyle="-")

ax.legend()

plt.gcf().autofmt_xdate()
plt.show()

<小时/> 如果一个人仍然有兴趣获得点图的图例，这里有一个方法：

sns.pointplot(ax=ax,x=x_col,y=y_col,data=df1,color='blue')
sns.pointplot(ax=ax,x=x_col,y=y_col,data=df2,color='green')
sns.pointplot(ax=ax,x=x_col,y=y_col,data=df3,color='red')

ax.legend(handles=ax.lines[::len(df1)+1], labels=["A","B","C"])

ax.set_xticklabels([t.get_text().split("T")[0] for t in ax.get_xticklabels()])
plt.gcf().autofmt_xdate()

plt.show()

Answer 2

我尝试使用亚当·B（Adam B）的答案，但是它对我没有用。相反，我发现了以下将图例添加到点状图的解决方法。

import matplotlib.patches as mpatches
red_patch = mpatches.Patch(color='#bb3f3f', label='Label1')
black_patch = mpatches.Patch(color='#000000', label='Label2')

在点绘图中，可以按照前面的答案中所述指定颜色。设置好与不同地块对应的这些补丁之后，

plt.legend(handles=[red_patch, black_patch])

图例应该出现在点图中。

Answer 3

Old question, but there's an easier way.

sns.pointplot(x=x_col,y=y_col,data=df_1,color='blue')
sns.pointplot(x=x_col,y=y_col,data=df_2,color='green')
sns.pointplot(x=x_col,y=y_col,data=df_3,color='red')
plt.legend(labels=['legendEntry1', 'legendEntry2', 'legendEntry3'])

This lets you add the plots sequentially, and not have to worry about any of the matplotlib crap besides defining the legend items.

Answer 4

这有点超出了最初的问题，但也建立在 @PSub 对更一般的东西的回应之上---我确实知道其中一些直接在 Matplotlib 中更容易，但是 Seaborn 的许多默认样式选项都非常好，所以我想弄清楚如何为一个点图（或其他 Seaborn 图）拥有多个图例，而无需立即进入 Matplotlib开始。

这是一种解决方案：


import numpy as np
import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt

# We will need to access some of these matplotlib classes directly
from matplotlib.lines import Line2D # For points and lines
from matplotlib.patches import Patch # For KDE and other plots
from matplotlib.legend import Legend

from matplotlib import cm

# Initialise random number generator
rng = np.random.default_rng(seed=42)

# Generate sample of 25 numbers
n = 25
clusters = []

for c in range(0,3):
    
    # Crude way to get different distributions
    # for each cluster
    p = rng.integers(low=1, high=6, size=4)
    
    df = pd.DataFrame({
        'x': rng.normal(p[0], p[1], n),
        'y': rng.normal(p[2], p[3], n),
        'name': f"Cluster {c+1}"
    })
    clusters.append(df)

# Flatten to a single data frame
clusters = pd.concat(clusters)

# Now do the same for data to feed into
# the second (scatter) plot... 
n = 8
points = []

for c in range(0,2):
    
    p = rng.integers(low=1, high=6, size=4)
    
    df = pd.DataFrame({
        'x': rng.normal(p[0], p[1], n),
        'y': rng.normal(p[2], p[3], n),
        'name': f"Group {c+1}"
    })
    points.append(df)

points = pd.concat(points)

# And create the figure
f, ax = plt.subplots(figsize=(8,8))

# The KDE-plot generates a Legend 'as usual'
k = sns.kdeplot(
    data=clusters,
    x='x', y='y',
    hue='name',
    shade=True,
    thresh=0.05,
    n_levels=2,
    alpha=0.2,
    ax=ax,
)

# Notice that we access this legend via the
# axis to turn off the frame, set the title, 
# and adjust the patch alpha level so that
# it closely matches the alpha of the KDE-plot
ax.get_legend().set_frame_on(False)
ax.get_legend().set_title("Clusters")
for lh in ax.get_legend().get_patches(): 
    lh.set_alpha(0.2)

# You would probably want to sort your data 
# frame or set the hue and style order in order
# to ensure consistency for your own application
# but this works for demonstration purposes
groups  = points.name.unique()
markers = ['o', 'v', 's', 'X', 'D', '<', '>']
colors  = cm.get_cmap('Dark2').colors

# Generate the scatterplot: notice that Legend is
# off (otherwise this legend would overwrite the 
# first one) and that we're setting the hue, style,
# markers, and palette using the 'name' parameter 
# from the data frame and the number of groups in 
# the data.
p = sns.scatterplot(
    data=points,
    x="x",
    y="y",
    hue='name',
    style='name',
    markers=markers[:len(groups)],
    palette=colors[:len(groups)],
    legend=False,
    s=30,
    alpha=1.0
)

# Here's the 'magic' -- we use zip to link together 
# the group name, the color, and the marker style. You
# *cannot* retreive the marker style from the scatterplot
# since that information is lost when rendered as a 
# PathCollection (as far as I can tell). Anyway, this allows
# us to loop over each group in the second data frame and 
# generate a 'fake' Line2D plot (with zero elements and no
# line-width in our case) that we can add to the legend. If
# you were overlaying a line plot or a second plot that uses
# patches you'd have to tweak this accordingly.
patches = []
for x in zip(groups, colors[:len(groups)], markers[:len(groups)]):
    patches.append(Line2D([0],[0], linewidth=0.0, linestyle='', 
                   color=x[1], markerfacecolor=x[1],
                   marker=x[2], label=x[0], alpha=1.0))

# And add these patches (with their group labels) to the new
# legend item and place it on the plot.
leg = Legend(ax, patches, labels=groups, 
             loc='upper left', frameon=False, title='Groups')
ax.add_artist(leg);

# Done
plt.show();

输出如下：

将传奇添加到Seaborn点图

4 个答案: