r - quanteda kwic 提取数字后跟百分比

Question

我有一些文本包含包含数字的短语，后跟一些符号。我想提取它们，例如，数字后跟百分比。使用 quanteda 包中的 kwic 函数似乎适用于数字作为正则表达式(例如 "\\d{1,}")。尽管如此，我没有找到如何使用 quanteda 提取它后跟一个百分号。以下文本可作为文本示例:

Thirteen (7%) of 187 patients acquired C. difficile in ICU-1, 9 (36%) of 25 on ICU-2 and 3 (5.9%) of 51 patients in BU. Eight (32%) developed diarrhoea attributable only to C. difficile and/ or toxin, and the remaining 17 (68%) were asymptomat- ic: none had pseudomembranous colitis.

Answer 1

原因是，当您直接在语料库或字符对象上调用 kwic() 时，它会将一些参数传递给 tokens()，这会影响标记化的发生方式，在上下文中的关键字分析之前。 (这记录在 ?kwic 的 ... 参数中。)

quanteda 中的默认标记化使用 stringi 词边界定义，因此:

tokens("Thirteen (7%) of 187")
# tokens from 1 document.
# text1 :
# [1] "Thirteen" "("        "7"        "%"        ")"        "of"       "187" 

如果您想使用更简单的空白标记器，可以使用:

tokens("Thirteen (7%) of 187", what = "fasterword")
# tokens from 1 document.
# text1 :
# [1] "Thirteen" "(7%)"     "of"       "187" 

因此，在 kwic() 中使用它的方法是:

kwic(s, "\\d+%", valuetype = "regex", what = "fasterword")

#  [text1, 2]                    Thirteen |  (7%)  | of 187 patients acquired C.             
# [text1, 12]    C. difficile in ICU-1, 9 | (36%)  | of 25 on ICU-2 and                      
# [text1, 19]           25 on ICU-2 and 3 | (5.9%) | of 51 patients in BU.                   
# [text1, 26]    51 patients in BU. Eight | (32%)  | developed diarrhoea attributable only to
# [text1, 41] toxin, and the remaining 17 | (68%)  | were asymptomat- ic: none had  

否则，您需要将正则表达式包装在 phrase() 函数中，并用空格分隔元素:

kwic(s, phrase("\\d+ %"), valuetype = "regex")

#   [text1, 3:4]             Thirteen( |  7 %  | ) of 187 patients acquired             
# [text1, 18:19]          in ICU-1, 9( | 36 %  | ) of 25 on ICU-2                       
# [text1, 28:29]       on ICU-2 and 3( | 5.9 % | ) of 51 patients in                    
# [text1, 39:40]         in BU. Eight( | 32 %  | ) developed diarrhoea attributable only
# [text1, 60:61] and the remaining 17( | 68 %  | ) were asymptomat- ic  

这种行为可能需要一些时间来适应，但这是确保用户完全控制搜索多 token 序列的最佳方式，而不是实现一种确定多 token 元素应该是什么的单一方法输入尚未被标记化时的顺序。