作用：

     创建二维、三维矩阵

格式：

      [X,Y] = meshgrid(x,y)
      [X,Y] = meshgrid(x)
      [X,Y,Z] = meshgrid(x,y,z)
      [X,Y,Z] = meshgrid(x)

eg:

>> [x,y]=meshgrid(1:1:3,5:1:6)x =1     2     31     2     3
y =5     5     56     6     6

> [x,y]=meshgrid(1:1:2)x =1     21     2
y =1     12     2


[x,y,z]=meshgrid(1:1:2)x(:,:,1) =1     21     2
x(:,:,2) =1     21     2
y(:,:,1) =1     12     2
y(:,:,2) =1     12     2
z(:,:,1) =1     11     1
z(:,:,2) =2     22     2


>> [x,y,z]=meshgrid(1:1:3,5:1:6,8:1:9)x(:,:,1) =1     2     31     2     3
x(:,:,2) =1     2     31     2     3
y(:,:,1) =5     5     56     6     6
y(:,:,2) =5     5     56     6     6
z(:,:,1) =8     8     88     8     8
z(:,:,2) =9     9     99     9     9