如何在同一矩阵中将一行的元素与其他行的元素进行比较 [英] How do I compare elements of one row with every other row in the same matrix

问题描述

我有矩阵:

a = [ 1 2 3 4;
      2 4 5 6;
      4 6 8 9]

，我想将每一行与其他两行一一比较.如果他们共享相同的密钥，那么结果将告诉他们拥有一个公共密钥.

and I want to compare every row with every other two rows one by one. If they share the same key then the result will tell they have a common key.

推荐答案

这是一个解决方案(可以推广到比问题中的样本更大的矩阵):

Here's one solution (which is generalizable to larger matrices than the sample in the question):

comparisons = nchoosek(1:size(a,1),2);
N = size(comparisons,1);
keys = cell(N,1);
for i = 1:N
  keys{i} = intersect(a(comparisons(i,1),:),a(comparisons(i,2),:));
end

函数 NCHOOSEK 用于生成所有行比较的 unique 组合.对于问题中的矩阵a，您将得到comparisons = [1 2; 1 3; 2 3]，这意味着我们需要比较行1和2，然后比较1和3，最后是2和3.keys是 INTERSECT 用于查找通用值(即键).对于问题中给出的矩阵a，您将获得keys = {[2 4], 4, [4 6]}.

The function NCHOOSEK is used to generate all of the unique combinations of row comparisons. For the matrix a in your question, you will get comparisons = [1 2; 1 3; 2 3], meaning that we will need to compare rows 1 and 2, then 1 and 3, and finally 2 and 3. keys is a cell array that stores the results of each comparison. For each comparison, the function INTERSECT is used to find the common values (i.e. keys). For the matrix a given in the question, you will get keys = {[2 4], 4, [4 6]}.

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