pandas 如何在 Seaborn facetgrid 条形图上添加图例
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How to add legend on Seaborn facetgrid bar plot
提问by neversaint
I have the following code:
我有以下代码：
import numpy as np
import pandas as pd
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
matplotlib.style.use('ggplot')
import seaborn as sns
sns.set(style="white")
# Create a dataset with many short random walks
rs = np.random.RandomState(4)
pos = rs.randint(-1, 2, (10, 5)).cumsum(axis=1)
pos -= pos[:, 0, np.newaxis]
step = np.tile(range(5), 10)
walk = np.repeat(range(10), 5)
df = pd.DataFrame(np.c_[pos.flat, step, walk],
columns=["position", "step", "walk"])
# Initialize a grid of plots with an Axes for each walk
grid = sns.FacetGrid(df, col="walk", hue="walk", col_wrap=5, size=5,
aspect=1)
# Draw a bar plot to show the trajectory of each random walk
grid.map(sns.barplot, "step", "position", palette="Set3").add_legend();
grid.savefig("/Users/mymacmini/Desktop/test_fig.png")
#sns.plt.show()
Which makes this plot:
这使得这个情节：
As you can see I get the legend wrong. How can I make it right?
如您所见，我弄错了图例。我怎样才能做到正确？
回答by CT Zhu
Some how there is one legend item for each of the subplot. Looks like if we want to have legend corresponds to the bars in each of the subplot, we have to manually make them.
每个子图都有一个图例项。看起来如果我们想让图例对应于每个子图中的条形，我们必须手动制作它们。
# Let's just make a 1-by-2 plot
df = df.head(10)
# Initialize a grid of plots with an Axes for each walk
grid = sns.FacetGrid(df, col="walk", hue="walk", col_wrap=2, size=5,
aspect=1)
# Draw a bar plot to show the trajectory of each random walk
bp = grid.map(sns.barplot, "step", "position", palette="Set3")
# The color cycles are going to all the same, doesn't matter which axes we use
Ax = bp.axes[0]
# Some how for a plot of 5 bars, there are 6 patches, what is the 6th one?
Boxes = [item for item in Ax.get_children()
if isinstance(item, matplotlib.patches.Rectangle)][:-1]
# There is no labels, need to define the labels
legend_labels = ['a', 'b', 'c', 'd', 'e']
# Create the legend patches
legend_patches = [matplotlib.patches.Patch(color=C, label=L) for
C, L in zip([item.get_facecolor() for item in Boxes],
legend_labels)]
# Plot the legend
plt.legend(handles=legend_patches)
回答by xApple
When the legend doesn't work out you can always make your own easily like this:
当图例不起作用时，您总是可以像这样轻松地制作自己的图例：
import matplotlib
name_to_color = {
'Expected': 'green',
'Provided': 'red',
'Difference': 'blue',
}
patches = [matplotlib.patches.Patch(color=v, label=k) for k,v in name_to_color.items()]
matplotlib.pyplot.legend(handles=patches)
