中文说明：模式识别中Parzen窗函数的实现，模拟对二维高斯分布的非参估计。窗函数有三种：高斯窗、指数窗、方窗
English Description：
The realization of Parzen window function in pattern recognition simulates the nonparametric estimation of two-dimensional Gaussian distribution. There are three kinds of window functions: Gaussian window, exponential window and square window