MATLAB：成对差异矩阵 [英] MATLAB: Matrix of pairwise differences

问题描述

我有值的NX1向量。我希望做的是创建一个N×N的矩阵，其中重$ P $每个值psents第i个第j值之间的差异 - 有点像一个大的相关性矩阵。我已经做了这一个循环，但我在寻找一个更优雅的方式使用MATLAB的矢量能力的方法，因为这种载体可能会相当大。

I have a Nx1 vector of values. What I would like to do is create a NxN matrix where each value represents the difference between the ith and jth value - sort of like a large correlation matrix. I've done with this with a loop but I'm looking for a more elegant way to approach using MATLAB's vectorization capabilities as this vector may get quite large.

推荐答案

怎么样

    diff__ = bsxfun(@minus,repmat(A,N,1),A');

可以是的有了一定的提高做

    diff__ = bsxfun(@minus,A,A');

一个小性能检查：

   N = 1000;
   v = rand(N,1);

   tic
   diff__ = bsxfun(@minus,repmat(v,N,1),v');
   toc

   tic
   diff__ = bsxfun(@minus,v,v');
   toc

结果

  Elapsed time is 105.343344 seconds.
  Elapsed time is 1.124946 seconds.

（Tim的数据检查：

(Tim's data check:

diff__ =

 0     2     6     4
-2     0     4     2
-6    -4     0    -2
-4    -2     2     0

）。

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