matplotlib入门（一）

基本用法

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-3,3,50)
y1=2*x+1
y2=x**2
plt.plot(x,y1)

plt.show()

figure图像

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-3,3,50)
y1=2*x+1
y2=x**2
plt.figure()
plt.plot(x,y1)

plt.figure()
plt.plot(x,y2)

plt.show()

plt.figure()默认自动从1开始编号。括号中可以自行设置参数：eg(num=3,figsize(8,5))

设置坐标轴

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-3,3,50)
y1=2*x+1
y2=x**2
#plt.figure()
#plt.plot(x,y1)

plt.figure(num=3,figsize=(8,5))
plt.plot(x,y2)
plt.plot(x,y1,color='red',linewidth=1.0,linestyle='--')
#坐标轴范围
plt.xlim((-1,2))
plt.ylim((-2,3))
#修改文字描述
plt.xlabel('I am x')
plt.ylabel('I am y')
#修改标尺
new_ticks = np.linspace(-1,2,6)
print(new_ticks)
plt.xticks(new_ticks)
plt.yticks([-2,-1.8,-1,1.22,3],
           [r'$really\ bad$',r'$bad\ \alpha$',r'$normal$',r'$good$','$really\ good$'])
plt.show()

#修改坐标轴位置
#spines:脊柱，指坐标轴四条边框。
#gca = 'get current axis'
ax=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)) #outward,axes
ax.spines['left'].set_position(('data',2))

legend图例

l1,=plt.plot(x,y2,label='up')
l2,=plt.plot(x,y1,color='red',linewidth=1.0,linestyle='--',label='down')
plt.legend(handles=[l1,],labels=['aaa',],loc='best')

Annotation标注

x0 = 1
y0 = 2*x0+1
plt.scatter(x0,y0,s=50,color='b') #散点
plt.plot([x0,x0],[y0,0],'k--',lw=2.5) #k:black --:style

plt.show()

tick能见度

import matplotlib.pyplot as plt
import numpy as np

x=np.linspace(-3,3,50)
y=0.1*x
plt.plot(x,y,linewidth=10)
plt.ylim(-2,2)

#gca = 'get current axis'
ax=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)) #outward,axes
ax.spines['left'].set_position(('data',2))

for label in ax.get_xticklabels()+ax.get_yticklabels():
    label.set_fontsize(12)
    label.set_bbox(dict(facecolor='white',edgecolor='None',alpha=0.2))

plt.show()