iMatlab

MATLAB中矩阵的嵌套

偶然发现了别人的仿真中一段精妙的代码（哈哈，这个不分享了，变量定义了好多，不方便大家阅读），查找它的原理，分享给大家。

Using Logicals in Array Indexing
A logical array index designates（指定了） the elements of an array A based on their position in the indexing array, B, not their value. In this masking type of operation, every true element in the indexing array is treated as a positional index into the array being accessed.

In the following example, B is a matrix of logical ones and zeros. The position of these elements in B determines which elements of A are designated by the expression A(B):
A = [1 2 3; 4 5 6; 7 8 9]
A =
     1     2     3
     4     5     6
     7     8     9


B = logical([0 1 0; 1 0 1; 0 0 1]);
B =
     0     1     0
     1     0     1
     0     0     1


C=A(B)

=  4

     2

     6
     9

得出的结果C是一个列向量。

很多人看见两个这种一个矩阵套在另一个矩阵的形式后就觉得不对，其实这种形式是存在的，但是注意B是类型，是一个逻辑变量构成的矩阵。

来源：爱兰松