numpy meshgrid

meshgrid 的使用方法：
[X,Y] = meshgrid(x,y) 将向量x和y定义的区域转换成矩阵X和Y，这两个矩阵可以用来表示mesh和surf的三维空间点以及两个变量的赋值。其中矩阵X的行向量是向量x的简单复制，而矩阵Y的列向量是向量y的简单复制。

Generate X and Y matrices for three-dimensional plots

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

Description：
[X,Y] = meshgrid(x,y) transforms the domain specified by vectors x and y into arrays X and Y, which can be used to evaluate functions of two variables and three-dimensional mesh/surface plots. The rows of the output array X are copies of the vector x; columns of the output array Y are copies of the vector y.
[X,Y] = meshgrid(x) is the same as [X,Y] = meshgrid(x,x).
[X,Y,Z] = meshgrid(x,y,z) produces three-dimensional arrays used to evaluate functions of three variables and three-dimensional volumetric plots.

Remarks：
The meshgrid function is similar to ndgrid except that the order of the first two input and output arguments is switched. That is, the statement [X,Y,Z] = meshgrid(x,y,z)
produces the same result as [Y,X,Z] = ndgrid(y,x,z)
Because of this, meshgrid is better suited to problems in two- or three-dimensional Cartesian space, while ndgrid is better suited to multidimensional problems that aren't spatially based.
meshgrid is limited to two- or three-dimensional Cartesian space.

From：网易博客
详细解释：help meshgrid
meshgrid用于从数组a和b产生网格。生成的网格矩阵A和B大小是相同的。它也可以是更高维的。
[A,B]=Meshgrid(a,b)
生成size(b)Xsize(a)大小的矩阵A和B。它相当于a从一行重复增加到size(b)行，把b转置成一列再重复增加到size(a)列。因此命令等效于：
A=ones(size(b))a;
B=b'ones(size(a))
如下所示：

a=[1:2]
a =
1 2
b=[3:5]
b =
3 4 5
[A,B]=meshgrid(a,b)
A =
1 2
1 2
1 2

B =
3 3
4 4
5 5

[B,A]=meshgrid(b,a)
B =
3 4 5
3 4 5

A =
1 1 1
2 2 2