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

问题描述

我有一个 Nx1 的值向量.我想做的是创建一个 NxN 矩阵，其中每个值代表第 i 个和第 j 个值之间的差异 - 有点像一个大的相关矩阵.我已经用一个循环完成了这个，但我正在寻找一种更优雅的方法来使用 MATLAB 的矢量化功能，因为这个矢量可能会变得非常大.

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');

可以绝对改进

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

?

一点性能检查:

   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.

(蒂姆的数据检查:

diff__ =

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

).

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