在数组中搜索值的组合 [英] Searching an array for combinations of values

问题描述

这应该是一个相当简单的问题，但是我很想听到一些独特的方法来解决这个问题.我正在使用Matlab，但是可行的C#解决方案也可以为我工作.

This should be a fairly simple question to answer, but I am interested to hear some unique ways to do it, so here goes. I am using Matlab, but a viable C# solution would work for me as well.

我有一个数组(23000行x 3列).每行是一组90个值中的3个值的组合.我想从这90个值中选择一个子集(例如10)，并找到这10个值中的任何3个是成员的行，然后返回行号.

I have an array (23000 rows x 3 columns). Each row is a combination of 3 values from a set of 90 values. I would like select a subset of these 90 values, say 10, and find the rows in which ANY 3 of these 10 values are members, and return the row number.

现在，我可以生成这10个值的所有3值组合的列表，然后在Matlab中使用ismember查找每个组合的行.但是，有其他方法还是更优雅的方法呢?

Now, I could generate a list of all the 3-value combinations of those 10 values, and then use ismember in Matlab to find the row for each combination. But is there a different or more elegant way?

或者，我可以使用a=sum(ismember(array, 'value'),2)生成逻辑向量，其中'value'出现在array中，并使用b=find(a)查找出现'value'的行索引.我可以为10的每个值执行此操作，但是现在问题出在这10个索引列表中，哪个索引出现3次或更多次?

Alternately, I could use a=sum(ismember(array, 'value'),2) to generate a logical vector where 'value' occurs in array, and use b=find(a) to find the row indices where 'value' occurs. I could do this for each value of the 10. But now the problem becomes, of these 10 lists of indices, which index occurs 3 or more times?

任何想法/评论/问题都值得赞赏.谢谢！

Any thoughts/comments/questions are appreciated. Thanks!

推荐答案

您对逻辑索引的建议几乎是正确的.

You were almost right with your suggestion of logical indexing.

使向量具有所有可能的值:

Make value a vector with all the possible values:

value = [1 2 3 4 5 6 7 8 9 10];

现在您可以一次在所有值上使用ismember.

Now you can use ismember on all the values at once.

logical_array = ismember(array, value);
num_matches = sum(logical_array,2);
rows_with_3_matches = find(num_matches==3);
logical_vector = num_matches==3;

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