sexy_and_drnd

代码说明：

  sexy函数可以将MATLAB符号表达式变成人们书写形式的表达式。 drnd函数是我写的可以生成服从任意有限离散分布的随机数。(sexy function can be MATLAB symbolic expression of the people into written form expression. Drnd function is I write can generate obey arbitrary finite discrete distribution of random numbers.)