1. Four methods
legend()
legend(handles, labels)
legend(handles=handles)
legend(labels)
1 legend()
Labels are automatically obtained through drawing ( Automatic detection of elements to be shown in the legend )
# 第一种方法
ax.plot([1, 2, 3], label='Inline label')
ax.legend()
# 第二种方法
line, = ax.plot([1, 2, 3])
line.set_label('Label via method')
ax.legend()
2 legend(handles, labels)
明确列出（Explicitly listing the artists and labels in the legend）
ax.legend([line1, line2, line3], ['label1', 'label2', 'label3'])
3 legend(handles=handles)
只列出handles（Explicitly listing the artists in the legend）
line1, = ax.plot([1, 2, 3], label='label1')
line2, = ax.plot([1, 2, 3], label='label2')
ax.legend(handles=[line1, line2])
4 legend(labels)
List labels only , not recommended, because the relationship between plot elements and labels is only implied by their order, and can be easily confused.
ax.plot([1, 2, 3])
ax.plot([5, 6, 7])
ax.legend(['First line', 'Second line'])
2. Important parameters
1 handlessequence of Artist, optional
The plot element to add to the legend.
A list of Artists (lines, patches) to be added to the legend.
2 labels list of str, optional
Labels next to plot elements.
A list of labels to show next to the artists.
3 loc (default: 'best'**)
Control the position of the legend (when setting the position of the legend, set this parameter first!!!)
4 bbox_to_anchor
2-tuple or 4-tuple. Generally, we use 2-tuple
to loccontrol the position box of the legend used together. This parameter can adjust any position of the legend.
**Note: use bbox_to_anchorwith and !loc
If it is 4-tuple , respectively represent
(x, y, width, height)x represents the horizontal axis, x=0 is the leftmost
y represents the y-axis, y=0 is the bottom side
width means width
height means height
one example:
#
loc='upper right', bbox_to_anchor=(0.5, 0.0, 0.5, 0.5)
If it is 2-tuple , respectively represent
(x, y)Note: When using loc=(x,y), x and y are not the actual values of x and y in the axis field, but the x-axis and y-axis are regarded as 1,
Namely: (x/(x_max-x_min), y/(y_max-y_min)) (normalized to 1);
The bigger the x, the more right
The larger the y, the more upward
one example:
# 如果不设置loc，默认将图例的【左下角】放在图的(0.5, 0.5)
bbox_to_anchor=(0.5, 0.5)
# 如果设置了loc
# 将图例的右上角点放在图的(0.5, 0.5)的位置【这个很重要】
loc='upper right', bbox_to_anchor=(0.5, 0.5)
# 将图例的右上角点放在图的(0.5, 0.5)【这个很重要】
loc='upper left', bbox_to_anchor=(0.5, 0.5)
5 prop None or or dictFontProperties
To set the font properties of the legend, it is generally most convenient to use a dictionary
prop={‘weight’: ‘bold’, ‘size’: 12}
6 ncols int, default: 1
the number of columns of the legend
7 markerfirst bool, default: True
If True, the legend marker will be placed to the left of the legend label.
If False, the legend marker will be placed to the right of the legend label.
8 frameon default: True
whether outside the legend frame
9 mode {“expand”, None}
If 'expand', the legend will expand horizontally to fill the axes area (or bbox_to_anchor if defining the size of the legend).
Summarize
1 Multiple subgraphs share a legend using
fig.legend()2 Multiple subgraphs [use a legend for each graph] use
ax.legend()3 position big call
loc4 Use
**bbox_to_anchor**the position of the legend to be set at will [it can be inside or outside the picture]
Learning link:
- https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.legend.html
- How does matplotlib control one of the positions of the legend? - Zhihu (zhihu.com)
- Matplotlib uses one legend for multiple subgraphs_matplotlib subgraphs share legend_Mepleleo's blog-CSDN blog