Matplot 第三部分

设置坐标轴：

修改坐标轴上的小标，以及显示坐标轴上的小标：

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

if 1:
    plt.figure(figsize=(14,12))
    x = np.linspace(0,10)
    plt.plot(x,x**3)

    new_ticks = np.linspace(0,10,20)
    plt.xticks(new_ticks)
    plt.yticks([0,500,1000],[r'$bad bad$',r'$normal alpha eta gamma$',r'$good$']) # $数学格式   是转移字符
    pass
plt.show()

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

if 1:
    plt.figure(figsize=(15,12))
    x = np.linspace(-np.pi/2,np.pi/2)
    plt.plot(x,x)
    plt.plot(x,np.cos(x))

    ax = plt.gca()
    ax.spines['top'].set_visible(False)
    ax.spines['right'].set_visible(False)

    ax.spines['bottom'].set_position(('data',0))
    ax.spines['left'].set_position(('data',0))


plt.show()

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

if 1:
    plt.figure(figsize=(15,12))
    x = np.linspace(-np.pi/2,np.pi/2)
    plt.plot(x,x,label='line1')
    plt.plot(x,np.cos(x),label='line2')
    plt.legend() #加上图例

    ax = plt.gca()
    ax.spines['top'].set_visible(False)
    ax.spines['right'].set_visible(False)

    ax.spines['bottom'].set_position(('data',0))
    ax.spines['left'].set_position(('data',0))


plt.show()

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

if 1:
    plt.figure(figsize=(15,12))
    x = np.linspace(-np.pi/2,np.pi/2)
    plt.plot(x,x,label='line1')
    plt.plot(x,np.cos(x),label='line2')
    plt.legend() #加上图例


    x0 = 0.739
    plt.scatter(x0,x0,s=50,color='b') #注 这里的 s 指的是 size 注意不可写size 只能写s
    plt.plot([x0,x0],[x0,0],'k--',linewidth=2.5)  #lw 指的是 linewidth,这个可以简写也可不简写

    #下面添加标注
    plt.annotate('y=x y=cos(x)的交点为 {}'.format([x0,x0]),fontproperties='SimHei',xy=(x0,x0),xytext=(x0+0.2,x0-0.05))






    ax = plt.gca()
    ax.spines['top'].set_visible(False)
    ax.spines['right'].set_visible(False)

    ax.spines['bottom'].set_position(('data',0))
    ax.spines['left'].set_position(('data',0))

#交点的位置是 0.739
if 0:
    #二分法
    if 0:
        def f(x):
            return np.cos(x) -x
        res = [0,np.pi/2]
        for i in range(10): #[0.7378447589729933, 0.739378739760879]
            mid = (res[0] + res[1])/2
            if f(res[0])*f(mid) < 0:
                res[1] = mid
            else:
                res[0] = mid
            print(res)
            pass

    #切线法
    if 1:
        def f(x):
            return x-np.cos(x)  #是单调递增的
        res = np.pi/2
        for i in range(10): #0.7390851332151607
            res = res - f(res)/(1 + np.sin(res))
        print(res)
        pass
    pass


plt.show()