【Python】matplotlib 双y轴绘制及合并图例
1.双y轴绘制 关键函数：twinx()
问题在于此时图例会有两个。
1 # -*- coding: utf-8 -*- 2 import numpy as np 3 import matplotlib.pyplot as plt 4 from matplotlib import rc 5 rc('mathtext', default='regular') 6 7 time = np.arange(10) 8 temp = np.random.random(10)*30 9 Swdown = np.random.random(10)*100-10 10 Rn = np.random.random(10)*100-10 11 12 fig = plt.figure() 13 ax = fig.add_subplot(111) 14 ax.plot(time, Swdown, '-', label = 'Swdown') 15 ax.plot(time, Rn, '-', label = 'Rn') 16 ax2 = ax.twinx() 17 ax2.plot(time, temp, '-r', label = 'temp') 18 ax.legend(loc=0) 19 ax.grid() 20 ax.set_xlabel("Time (h)") 21 ax.set_ylabel(r"Radiation ($MJ\,m^{-2}\,d^{-1}$)") 22 ax2.set_ylabel(r"Temperature ($^\circ$C)") 23 ax2.set_ylim(0, 35) 24 ax.set_ylim(-20,100) 25 ax2.legend(loc=0) 26 plt.savefig('0.png')
每个句柄对应一个图例。
2. 合并图例
1） 仅使用一个轴的legend()函数
1 # -*- coding: utf-8 -*- 2 import numpy as np 3 import matplotlib.pyplot as plt 4 from matplotlib import rc 5 rc('mathtext', default='regular') 6 7 time = np.arange(10) 8 temp = np.random.random(10)*30 9 Swdown = np.random.random(10)*100-10 10 Rn = np.random.random(10)*100-10 11 12 fig = plt.figure() 13 ax = fig.add_subplot(111) 14 15 lns1 = ax.plot(time, Swdown, '-', label = 'Swdown') 16 lns2 = ax.plot(time, Rn, '-', label = 'Rn') 17 ax2 = ax.twinx() 18 lns3 = ax2.plot(time, temp, '-r', label = 'temp') 19 20 # added these three lines 21 lns = lns1+lns2+lns3 22 labs = [l.get_label() for l in lns] 23 ax.legend(lns, labs, loc=0) 24 25 ax.grid() 26 ax.set_xlabel("Time (h)") 27 ax.set_ylabel(r"Radiation ($MJ\,m^{-2}\,d^{-1}$)") 28 ax2.set_ylabel(r"Temperature ($^\circ$C)") 29 ax2.set_ylim(0, 35) 30 ax.set_ylim(-20,100) 31 plt.savefig('0.png')
可以看到y1轴和y2轴的图例已经合并了
2）使用figure.legend()
1 # -*- coding: utf-8 -*- 2 import numpy as np 3 import matplotlib.pyplot as plt 4 5 x = np.linspace(0,10) 6 y = np.linspace(0,10) 7 z = np.sin(x/3)**2*98 8 9 fig = plt.figure() 10 ax = fig.add_subplot(111) 11 ax.plot(x,y, '-', label = 'Quantity 1') 12 13 ax2 = ax.twinx() 14 ax2.plot(x,z, '-r', label = 'Quantity 2') 15 fig.legend(loc=1) 16 17 ax.set_xlabel("x [units]") 18 ax.set_ylabel(r"Quantity 1") 19 ax2.set_ylabel(r"Quantity 2") 20 21 plt.savefig('0.png')
可以看到图例位置不对，已经出界，需要使用bbox_to_anchor和bbox_transform设置。
fig.legend(loc=1, bbox_to_anchor=(1,1), bbox_transform=ax.transAxes)
1 # -*- coding: utf-8 -*- 2 import numpy as np 3 import matplotlib.pyplot as plt 4 5 x = np.linspace(0,10) 6 y = np.linspace(0,10) 7 z = np.sin(x/3)**2*98 8 9 fig = plt.figure() 10 ax = fig.add_subplot(111) 11 ax.plot(x,y, '-', label = 'Quantity 1') 12 13 ax2 = ax.twinx() 14 ax2.plot(x,z, '-r', label = 'Quantity 2') 15 fig.legend(loc=1, bbox_to_anchor=(1,1), bbox_transform=ax.transAxes) 16 17 ax.set_xlabel("x [units]") 18 ax.set_ylabel(r"Quantity 1") 19 ax2.set_ylabel(r"Quantity 2") 20 21 plt.savefig('0.png')
可以看到图例已经正常了。
