nlp - 雪球词干 : defining Null Region

Question

我正在尝试理解雪球词干算法。 HW90有一个类似的问题和例子，但不是我的。该算法使用两个区域 R1 和 R2，定义如下:

R1 is the region after the first non-vowel following a vowel, or is the null region at the end of the word if there is no such non-vowel.

R2 is the region after the first non-vowel following a vowel in R1, or is the null region at the end of the word if there is no such non-vowel.

http://snowball.tartarus.org/texts/r1r2.html

我不明白，“单词末尾的空区域”是什么。有人能给我一些例子吗？

Answer 1

Null Region 表示空白区域，没有字母。您错过了 documentation page 中的示例:

Below, R1 and R2 are shown for a number of English words,

b   e   a   u   t   i   f   u   l
                  |<------------->|    R1
                          |<----->|    R2

Letter t is the first non-vowel following a vowel in beautiful, so R1 is iful. In iful, the letter f is the first non-vowel following a vowel, so R2 is ul.

b   e   a   u   t   y
                  |<->|    R1
                    ->|<-  R2 

In beauty, the last letter y is classed as a vowel. Again, letter t is the first non-vowel following a vowel, so R1 is just the last letter, y. R1 contains no non-vowel, so R2 is the null region at the end of the word.

b   e   a   u
            ->|<-  R1
            ->|<-  R2