Matplotlib的使用

import matplotlib.pyplot as pltimport numpy as npx = np.linspace(-3,3,50)y1 = x*2+1y2 = x**2plt.figure()l1, = plt.plot(x,y1,label='up')l2, = plt.plot(x,y2,color='r',linewidth=1.0,linestyle='--',label='down')plt.xlabel('I am x')plt.ylabel("I am Y")#gca = get current axisax = plt.gca()ax.spines['right'].set_color('none')ax.spines['top'].set_color('none')ax.xaxis.set_ticks_position('bottom')ax.yaxis.set_ticks_position('left')ax.spines['bottom'].set_position(('data',0))ax.spines['left'].set_position(('data',0))plt.legend(handles=[l1,l2],labels=['a','b'],loc='best')x0 = 1y0 = 2*x0 + 1#plt一个点plt.scatter(x0,y0,s=50,color='green')plt.plot([x0,x0],[y0,0],'k--',lw=1.5)#黑色的虚线，简写#标注plt.annotate(r'$2x+1=%s$'%y0,xy=(x0,y0),xycoords='data',xytext=(+30,-30),             textcoords='offset points',fontsize=16,arrowprops=dict(arrowstyle='->',                                                        connectionstyle='arc3,rad=.2'))           plt.text(-3.7,3,r'$This\ is\ some\ text$',fontdict={'size':16,'color':'orange'})plt.show()