通过向量中的索引寻址多个范围 [英] Addressing multiple ranges via indices in a vector

问题描述

首先，可以使用for循环轻松解决此问题.但是，我试图强迫/自学向量矢量思维，以充分利用Matlab的优势.

To begin, this problem is easily solvable with a for-loop. However, I'm trying to force/teach myself to think vector-wise to take advantage of what Matlab does best.

简化，这是问题的说明:

Simplified, here is the problem explanation:

• 我有一个带有数据的向量.
• 我有一个2xN的起始/终止索引数组，代表向量中有趣数据的范围.
• 我想对每个范围进行计算，得出一个数字(N个结果，对应于每个开始/停止范围.)

在代码中，这是我最后想要的伪示例:

In code, here's a pseudoexample of what I'd like to have at the end:

A = 1:10000;
startIndicies = [5 100 1000];
stopIndicies = [10 200 5000];
...
calculatedResults = [func(A(5:10)) func(A(100:200)) func(A(1000:5000))]

A和开始/停止索引数组的长度是可变的.

The length of A, and of the start/stop index array is variable.

就像我说的那样，我可以使用for循环轻松解决此问题.但是，由于可以与大型数据集一起使用，因此我想知道是否有没有for循环的好的解决方案.

Like I said, I can easily solve this with a for loop. However since could be used with a large data set, I'd like to know if there's a good solution without a for loop.

推荐答案

这是一个可能的解决方案，尽管我不会将其称为完全矢量化的解决方案，而是一个一个内衬一个.

Here is one possible solution, although, I won't call it a fully vectorized solution, rather a one liner one.

 out = cellfun(@(i,j) fun(A(i:j)), num2cell(startIndicies), num2cell(stopIndicies) );

或者，如果您打算提供同类输出，

or, if you plan to have homogeneous outputs,

 out = arrayfun(@(i,j) fun(A(i:j)), startIndicies, stopIndicies);

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