安装了统计软件包，不知道为啥还出错？
n3 = exprnd(5,2,3)
??? Error using ==> exprnd
Too many input arguments.


下面是help 的结果
help exprnd
   Random samples from the exponential distribution with expectation a
   and variance a^2.

   INPUTS
     a       [double]    m*n matrix of positive parameters

   OUTPUT
     rnd     [double]    m*n matrix, independent draws from the exponential
                         distribution rnd(j,j) has expectation a(i,j) and     
                         variance a(i,j)^2.   

   ALGORITHM  
     Inverse transform sampling.

   SPECIAL REQUIREMENTS
     None.