Python绘制正态分布曲线

  使用Python绘制正态分布曲线，借助matplotlib绘图工具；

[f(x) = dfrac{1}{sqrt{2pi}sigma}exp(-dfrac{(x-mu)^2}{2sigma^2}) ]

#-*-coding:utf-8-*-
"""
python绘制标准正态分布曲线
"""
# ==============================================================
import numpy as np
import math
import matplotlib.pyplot as plt


def gd(x, mu=0, sigma=1):
    """根据公式，由自变量x计算因变量的值

    Argument:
        x: array
            输入数据（自变量）
        mu: float
            均值
        sigma: float
            方差
    """
    left = 1 / (np.sqrt(2 * math.pi) * np.sqrt(sigma))
    right = np.exp(-(x - mu)**2 / (2 * sigma))
    return left * right


if __name__ == '__main__':
    #  自变量
    x = np.arange(-4, 5, 0.1)
    #  因变量（不同均值或方差）
    y_1 = gd(x, 0, 0.2)
    y_2 = gd(x, 0, 1.0)
    y_3 = gd(x, 0, 5.0)
    y_4 = gd(x, -2, 0.5)

    #  绘图
    plt.plot(x, y_1, color='green')
    plt.plot(x, y_2, color='blue')
    plt.plot(x, y_3, color='yellow')
    plt.plot(x, y_4, color='red')
    #  设置坐标系
    plt.xlim(-5.0, 5.0)
    plt.ylim(-0.2, 1)

    ax = plt.gca()
    ax.spines['right'].set_color('none')
    ax.spines['top'].set_color('none')
    ax.xaxis.set_ticks_position('bottom')
    ax.spines['bottom'].set_position(('data', 0))
    ax.yaxis.set_ticks_position('left')
    ax.spines['left'].set_position(('data', 0))

    plt.legend(labels=['$mu = 0, sigma^2=0.2$', '$mu = 0, sigma^2=1.0$', '$mu = 0, sigma^2=5.0$', '$mu = -2, sigma^2=0.5$'])
    plt.show()