三、数据可视化：matplotlib.pyplot (mp)
1、基本绘图函数
mp.plot(水平坐标数组, 垂直坐标数组)
x: [1 2 3 4]
y: [5 6 7 8]
代码：plt1.py

import numpy as np
import matplotlib.pyplot as mp
x = np.linspace(-np.pi, np.pi, 1000)
cos_y = np.cos(x) / 2
sin_y = np.sin(x)
mp.plot(x, cos_y)
mp.plot(x, sin_y)
mp.show()

mp.plot(..., linestyle=线型, linewidth=线宽（默认为2）,
    color=颜色)

代码：plt2.py

import numpy as np
import matplotlib.pyplot as mp
x = np.linspace(-np.pi, np.pi, 1000)
cos_y = np.cos(x) / 2
sin_y = np.sin(x)
mp.plot(x, cos_y, linestyle='--', linewidth=6, color='dodgerblue')
mp.plot(x, sin_y, linestyle=':', linewidth=3, color='orangered')
mp.show()

mp.xlim(左边界, 右边界)
mp.ylim(底边界, 顶边界)

代码：plt3.py

import numpy as np
import matplotlib.pyplot as mp
x = np.linspace(-np.pi, np.pi, 1000)
cos_y = np.cos(x) / 2
sin_y = np.sin(x)
mp.xlim(x.min(), x.max())  # 左右边界
mp.ylim(sin_y.min(), sin_y.max())  # 上下边界
mp.plot(x, cos_y, linestyle='--', linewidth=6, color='dodgerblue')
mp.plot(x, sin_y, linestyle=':', linewidth=3, color='orangered')
mp.show()

mp.xticks(刻度位置数组, 刻度文本数组) 水平方向
mp.yticks(刻度位置数组, 刻度文本数组) 垂直方向

代码：plt4.py

import numpy as np
import matplotlib.pyplot as mp
x = np.linspace(-np.pi, np.pi, 1000)
cos_y = np.cos(x) / 2
sin_y = np.sin(x)
mp.xlim(x.min() * 1.1, x.max() * 1.1)
mp.ylim(sin_y.min() * 1.1, sin_y.max() * 1.1)
mp.xticks([-np.pi, -np.pi / 2, 0, np.pi / 2, np.pi * 3 / 4,
           np.pi],
          [r'$-\pi$', r'$-\frac{\pi}{2}$', r'$0$',
           r'$\frac{\pi}{2}$', r'$\frac{3\pi}{4}$',
           r'$\pi$'])
mp.yticks([-1, -0.5, 0.5, 1])
mp.plot(x, cos_y, linestyle='-', linewidth=2,
        color='dodgerblue')
mp.plot(x, sin_y, linestyle='-', linewidth=2,
        color='orangered')
mp.show()

ax = mp.gca() # 获取当前坐标轴
ax.spines['left'].set_position(('data', 0)) 设置坐标轴的位置
ax.spines['left'].set_color(颜色)

代码：plt5.py

mp.plot(…, label=图例文本)
mp.legend(loc=‘upper left’)
代码：plt6.py

mp.scatter(水平坐标数组, 垂直坐标数组,
marker=点型， s=大小, edgecolor=勾边色,
facecolor=填充色, zorder=Z序)
代码：plt7.py

mp.annotate(
备注文本,
xy=目标位置,
xycoords=目标坐标系,
xytext=文本位置, # 常用偏移位置
textcoords=文本坐标系, # 常用偏移坐标系 offset points
fontsize=字体大小,
arrowprops=箭头属性)
代码：plt8.py

![import numpy as np
import matplotlib.pyplot as mp
x = np.linspace(-np.pi, np.pi, 1000)
cos_y = np.cos(x) / 2
sin_y = np.sin(x)

xo = np.pi * 3 / 4
yo_cos = np.cos(xo) / 2
yo_sin = np.sin(xo)

mp.xlim(x.min() * 1.1, x.max() * 1.1)
mp.ylim(sin_y.min() * 1.1, sin_y.max() * 1.1)

# 设置坐标刻度
mp.xticks(\[-np.pi, -np.pi / 2, 0, np.pi / 2, np.pi * 3 / 4,
           np.pi\],
          \[r'$-\pi$', r'$-\frac{\pi}{2}$', r'$0$',
           r'$\frac{\pi}{2}$', r'$\frac{3\pi}{4}$',
           r'$\pi$'\])
mp.yticks(\[-1, -0.5, 0.5, 1\])

# 设置坐标系， 变为十字坐标系
ax = mp.gca()
ax.spines\['left'\].set_position(('data', 0))  # 将坐标轴的左边框移动到0
ax.spines\['bottom'\].set_position(('data', 0))  # 将坐标轴的上边框移动的0
ax.spines\['right'\].set_color('None')  # 将坐标轴的右边框颜色设置为无
ax.spines\['top'\].set_color('None')  # 将坐标轴的上边框颜色设置为无

# 设置图例
mp.plot(x, cos_y, linestyle='-', linewidth=2,
        color='dodgerblue', label=r'$y=\frac{1}{2}cos(x)$')
mp.plot(x, sin_y, linestyle='-', linewidth=2,
        color='orangered', label=r'$y=sin(x)$')
mp.legend(loc='upper left')

# scatter
mp.scatter(\[xo, xo\], \[yo_cos, yo_sin\], s=60,
           edgecolor='limegreen', facecolor='white',
           zorder=3)
mp.plot(\[xo, xo\], \[yo_cos, yo_sin\], linestyle='--',
        linewidth=1, color='limegreen')

# 对两个点添加注释
mp.annotate(
    r'$\frac{1}{2}cos(\frac{3\pi}{4})=-\frac{\sqrt{2}}{4}$',  # frac{}{}为分数 sqrt{}为根号
    xy=(xo, yo_cos), xycoords='data',
    xytext=(-90, -40), textcoords='offset points',
    fontsize=14,
    arrowprops=dict(arrowstyle='->',
                    connectionstyle='arc3, rad=.2'))
mp.annotate(
    r'$sin(\frac{3\pi}{4})=\frac{\sqrt{2}}{2}$',
    xy=(xo, yo_sin), xycoords='data',
    xytext=(20, 20), textcoords='offset points',
    fontsize=14,
    arrowprops=dict(arrowstyle='->',
                    connectionstyle='arc3, rad=.2'))
mp.show()