我怎样才能在MATLAB中为这个矢量生成一个映射关键字？ [英] How can I generate a map key for this vector in MATLAB?

问题描述

我有一个功能正在查看一些元素。每个元素都是8x1列向量的形式。向量中的每个条目都是一个小于1000的整数。每次我看到这样一个向量时，我想在检查该向量不在该列表中之后，将其添加到已经看过向量的列表中。该函数将检查大约100,000个这样的向量。

原来我试过用 ismember（v'，M，'rows'），但发现这很慢。下一步，我试过：

  found = containers.Map（'KeyType'，'double'，'ValueType'，'any'） ; 
  

然后每次检查一个新的向量 v ，计算：

  key = dot（v，[1000000000000000000000 1000000000000000000 1000000000000000 ... 
 1000000000000 1000000000 1000000 1000 1 ]）; 
  

然后检查 isKey（found，key） 。如果钥匙不在容器中，那么 found（key）= 1 。

这看起来像一个漂亮糟糕的解决方案，尽管它的运行速度远远超过 ismember 。任何帮助/建议将不胜感激。编辑：也许它会更好地使用 mat2str 来生成关键，而不是这个愚蠢的点产品？

解决方案

最简单的方法来生成一个键/使用 char将整数值的向量转换为字符数组 。由于您的整数值永远不会超过1000，并且 char 可以接受0到65535之间的数字值（对应于Unicode字符），所以这会为您提供一个唯一的8字符密钥每一个独特的8乘1向量。下面是一个例子：

  found = containers.Map（'KeyType'，'char'，'ValueType'，'any'） ; 
 
 v = randi（1000，[8 1]）; ％示例向量
 key = char（v）; 
 if〜isKey（found，key）
 found（key）= 1; 
 end 
  

I have a function that is looking at a number of elements. Each element is of the form of an 8x1 column vector. Each entry in the vector is an integer less than 1000. Every time I see such a vector, I'd like to add it to a list of "already seen" vectors, after checking to see that the vector is not already on this list. The function will examine on the order of ~100,000 such vectors.

Originally I tried using ismember(v', M, 'rows'), but found this to be very slow. Next I tried:

found = containers.Map('KeyType', 'double', 'ValueType', 'any');

Then each time I examine a new vector v, compute:

key = dot(v, [1000000000000000000000 1000000000000000000 1000000000000000 ...
              1000000000000 1000000000 1000000 1000 1]);

Then check isKey(found, key). If the key is not in the container, then found(key) = 1.

This seems like a pretty lousy solution, even though it does run considerably faster than ismember. Any help/suggestions would be greatly appreciated.

EDIT: Perhaps it would be better to use mat2str to generate the key, rather than this silly dot product?

解决方案

The easiest way to generate a key/hash in your case would be to just convert the vector of integer values to a character array using char. Since your integer values never go above 1000, and char can accept numeric values from 0 to 65535 (corresponding to Unicode characters), this will give you a unique 8-character key for every unique 8-by-1 vector. Here's an example:

found = containers.Map('KeyType', 'char', 'ValueType', 'any');

v = randi(1000, [8 1]);  % Sample vector
key = char(v);
if ~isKey(found, key)
  found(key) = 1;
end

这篇关于我怎样才能在MATLAB中为这个矢量生成一个映射关键字？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！