A(输入)在最常见的输入中做了什么？

Question

我正在使用简单的矩阵并得到一些奇怪的东西.

A = 
2 3 
5 6 
8 9

而我这样做了.

A([1 3],[1 2 2]) 

ans = 
2 3 3 
8 9 9

而我这样做了.

A([1 3],[1 2]) 

ans = 
2 3 
8 9

我无法弄清楚为什么MatLab有这个结果.

或者,更一般地说,A(输入)在最常见的输入中做了什么？

Answer 1

A(input)从传递的索引生成矩阵input.简单的例子就是

A(1,1) # select the element from first row, first column
A(2,:) # select the complete second row
A(:,2) # select the complete second column
A([1 2],1) # select the element from the first and second row and first column each

从你的例子

A([1 3],[1 2 2]) # Select elements from first row and first and two times second column 
                 #as well as third row with first and two times second column.

类似

A([1 3],[1 2])  # Select elements from first row and first and second column
                # as well as third row and first and second column