笛卡尔乘积的Matlab矢量化

Question

假设我有两个数组X和Y，我需要一个矩阵M(i，j) = some_func(X(i)，Y(j))。我怎样才能在不使用循环的情况下得到它呢？

Answer 1

最好的答案是使用bsxfun，如果它是一个选项。根据bsxfun的帮助，它可以在任何通用的二元函数上工作，只要：

  FUNC can also be a handle to any binary element-wise function not listed
    above. A binary element-wise function in the form of C = FUNC(A,B)
    accepts arrays A and B of arbitrary but equal size and returns output
    of the same size. Each element in the output array C is the result
    of an operation on the corresponding elements of A and B only. FUNC must
    also support scalar expansion, such that if A or B is a scalar, C is the
    result of applying the scalar to every element in the other input array.

如果你的函数只接受标量输入，那么循环是一个简单的选择。

Answer 2

很难回答你模糊的问题，这最终取决于你的功能。您可以执行的操作是使用meshgrid，然后执行操作，通常使用点运算符

例如：

x = 1:5;
y = 1:3;

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

M = X.^Y;