“英语的孤立符号概率"的含义是什么? [英] What is the meaning of "isolated symbol probabilities of English"

问题描述

在笔记中，我找到了这个短语:

In a note I found this phrase:

使用孤立的英语符号概率，您可以了解英语的熵.

Using isolated symbol probabilities of English language, you can find out the entropy of the language.

孤立符号概率"实际上是什么意思?这与信息源的熵有关.

What is actually meant by "isolated symbol probabilities"? This is related to the entropy of an information source.

推荐答案

了解笔记来自何处以及上下文是什么会很有帮助，但是即使没有这个，我也很确定这只是意味着他们使用单个符号的频率(例如字符)作为熵的基础，而不是例如联合概率(字符序列的)或条件概率(一个特定角色跟随另一个角色).

It would be helpful to know where the note came from and what the context is, but even without that I am quite sure this simply means that they use the frequency of individual symbols (e.g. characters) as the basis for entropy, rather than for example the joint probability (of character sequences), or the conditional probability (of one particular character to follow another).

因此，如果您有一个字母X = {a，b，c，...，z}，并且每个字符出现在文本中的概率为P(a)，P(b)，...(例如， (在数据示例中找到的频率上)，您可以通过分别为每个字符x 计算-P(x)* log(P(x))来计算熵，然后取所有.然后，显然，您将使用每个字符的概率，而不是每个字符在上下文中的概率.

So if you have an alphabet X={a,b,c,...,z} and a probability P(a), P(b),... for each character to appear in text (e.g. based on the frequency found in a data example), you'd compute the entropy by computing -P(x) * log(P(x)) for each character x individually and then taking the sum of all. Then, obviously, you'd have used the probability of each character in isolation, rather than the probability of each character in context.

但是请注意，您发现的注释中的 symbol 术语不一定指代字符.它可能指的是单词或其他文本单元.不过，他们提出的观点是，他们将熵的经典公式应用于单个事件的概率(字符，单词等)，而不是复杂事件或条件事件的概率. >

Note, however, that the term symbol in the note you found does not necessarily refer to characters. It might refer to words or other units of text. Nevertheless, the point they are making is that they apply the classical formula for entropy to probabilities of individual events (characters, words, whatever), not probabilities of complex or conditional events.

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