图底部带有twinx的matplotlib图例

Question

我正在尝试在两个图下绘制一个图例(使用twinx创建)。我希望图例绘制在底部的中心与4列对齐。到目前为止还没有成功。我如何制作关于整个绘图的图例，而不仅仅是单个轴对象。有什么帮助吗？

import matplotlib.pyplot as plt;
import numpy as np;
from matplotlib import rc;

filename = 'ml.pdf';

fig, ax1 = plt.subplots(frameon=False);
rc('mathtext', default='regular');
rc('lines',lw=2.6);
rc('lines',mew=2.4);
rc('text', usetex=True);
x = np.array([5,10,20,50]);

dp_g = np.array([23.43, 29.93, 36.50, 46.07]);
mr_g  = np.array([25.33, 31.83, 38.39, 47.75]);
md_g  = np.array([24.94, 31.33, 37.80, 47.10]);
sb_g  = np.array([27.01, 34.86, 43.18, 54.35]);

lns1 = ax1.plot(x,dp_g,'bs:', label="MD\n($\lambda$=.8)");
lns2 = ax1.plot(x,mr_g,'bs--',label="MR\n($\lambda$=.1)");
lns3 = ax1.plot(x,md_g,'bs-.',label='MD');
lns4 = ax1.plot(x,sb_g,'bs-',label="SB\n($\gamma$=.1)");


ax1.set_ylabel('CG ($\times$ 100)',color='b',size=14);
ax1.set_ylim([20,57]);
ax1.set_xlim([4,51]);
ax1.set_xticks(x);
ax1.tick_params(axis='y', which=u'both', length=0, labelsize=14, colors='b');
ax1.tick_params(axis='x', which=u'both', length=0, labelsize=14);

ax2 = ax1.twinx();
dp_d = np.array([18.84, 19.55, 20.09, 20.08]);
mr_d  = np.array([19.42, 19.73, 20.06, 20.04]);
md_d  = np.array([19.02, 19.75, 20.28, 20.29]);
sb_d  = np.array([20.81, 19.77, 19.20, 19.03]);


lns6 = ax2.plot(x,dp_d,'rv:',label="MD\n($\lambda$=.8)");
lns7 = ax2.plot(x,mr_d,'rv--',label="MR\n($\lambda$=.1)");
lns8 = ax2.plot(x,md_d,'rv-.',label='MD');
lns9 = ax2.plot(x,sb_d,'rv-',label="SB\n($\gamma$=.1)");

lns = lns1 + lns2 + lns3 + lns4 + lns6 + lns7 + lns8 + lns9;
labs = [l.get_label() for l in lns];

ax2.set_ylabel('LD ($\times$ 100)',color='r',size=14);
ax2.set_ylim([15,23]);
ax2.set_xlim([4,51]);
ax2.set_xticks(x);
ax2.tick_params(axis='y', which=u'both', length=0, labelsize=14, colors='r');
ax2.tick_params(axis='x', which=u'both', length=0, labelsize=14);

ax1.set_xlabel('\# of items',size=14);
borderaxespad=2.5, ncol = 1, fontsize='11.5');
lgd = ax1.legend(lns, labs, bbox_to_anchor=(1.01,1.0), loc='lower center', borderaxespad=2.5, ncol = 4, fontsize='14');

fig.savefig(filename,format='pdf',transparent=True, bbox_extra_artists=(lgd,), bbox_inches='tight');

Answer 1

除了虚线borderaxespad=2.5, ncol = 1, fontsize='11.5');之外，我相信您想要做的就是从图例定义中删除bbox_to_anchor=(1.01, 1.0)。这样做会将图例放在绘图的底部中心(但是图例非常宽，因此它将跨越整个绘图的宽度)。