从 xarray.dataArray 绘图时选择 artists/handles 作为图例

Question

我正在从 xarray DataArray 绘制一个 facet plot，每个 plot 上有多条线。我想为每个情节都有一个图例，但它应该只包含某些行。我使用 .legend() 应该给出我想在图例中拥有的数据，但是当我从 xarray DataArray 绘图时，我不知道该怎么做。

这里作为示例代码：

import matplotlib.pyplot as plt
import xarray as xr
import numpy as np
import pandas as pd
           
data1 = np.random.randn(4, 4,3)
loc= np.linspace(1,3,3)
type = ["a", "b", "c", "d"]
            
times = pd.date_range("2000-01-01", periods=4)
foo = xr.DataArray(data1, coords=[times, type, loc], dims=["time", "type","loc"])
    
t=foo.plot.line(x="time", col="loc", linewidth= 5, col_wrap=3)
for i, ax in enumerate(t.axes.flat):
    ax.legend(('labelc','labeld'))

在这里，我希望标签实际适合数据 c 和 d

ax.legend 应该是这样工作的：

ax.legend([line1, line2, line3], ['label1', 'label2', 'label3'])

我已经像下面这样尝试过，但无法正常工作：

for i, ax in enumerate(t.axes.flat):
    ax.legend(foo[:,2:,i],('labelc','labeld'))

Answer 1

我们可以检索 figure-level 个图例条目并过滤它们以获得所需的条目：

import matplotlib.pyplot as plt
import xarray as xr
import numpy as np
import pandas as pd
           
data1 = np.random.randn(4, 4, 3)
locs = np.linspace(1, 3, 3)
types = ["a", "b", "c", "d"]
            
times = pd.date_range("2000-01-01", periods=4)
foo = xr.DataArray(data1, coords=[times, types, locs], dims=["time", "type","loc"])
    
t=foo.plot.line(x="time", col="loc", linewidth= 5, col_wrap=3)

#define list which entries to show in subplot legends 
to_keep = ["b", "d"]
#retrieve global handles and labels
labels = t._hue_var.to_numpy()
handles = t._mappables[-1]

#create a dictionary of labels and handles while filtering unwanted entries
label_dic = {l:h  for l, h in zip(labels, handles) if l in to_keep}

#create legend entries as you intended with your code
for ax in t.axes.flat:
    ax.legend(label_dic.values(), label_dic.keys(), loc="best")
plt.show()

示例输出：

检索图例条目的代码是从 source code for def add_legend() 中提取的。

另请注意，我已将您的变量 type 更改为 types，因为它隐藏了 Python 函数 type()。

从 xarray.dataArray 绘图时选择 artists/handles 作为图例

choosing artists/handles for legend when plotting from xarray.dataArray

plot

matplotlib

legend

facet

python-xarray