Python - 频率分布

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  简述

  在文本处理过程中，经常需要计算一个词在正文中出现的频率。这可以通过应用word_tokenize()函数并将结果附加到列表中以保持单词的计数，如下面的程序所示。

  
  from nltk.tokenize import word_tokenize
  from nltk.corpus import gutenberg
  sample = gutenberg.raw("blake-poems.txt")
  token = word_tokenize(sample)
  wlist = []
  for i in range(50):
      wlist.append(token[i])
  wordfreq = [wlist.count(w) for w in wlist]
  print("Pairs\n" + str(zip(token, wordfreq)))
  

  当我们运行上述程序时，我们得到以下输出 -

  
  [([', 1), (Poems', 1), (by', 1), (William', 1), (Blake', 1), (1789', 1), (]', 1), (SONGS', 2), (OF', 3), (INNOCENCE', 2), (AND', 1), (OF', 3), (EXPERIENCE', 1), (and', 1), (THE', 1), (BOOK', 1), (of', 2), (THEL', 1), (SONGS', 2), (OF', 3), (INNOCENCE', 2), (INTRODUCTION', 1), (Piping', 2), (down', 1), (the', 1), (valleys', 1), (wild', 1), (,', 3), (Piping', 2), (songs', 1), (of', 2), (pleasant', 1), (glee', 1), (,', 3), (On', 1), (a', 2), (cloud', 1), (I', 1), (saw', 1), (a', 2), (child', 1), (,', 3), (And', 1), (he', 1), (laughing', 1), (said', 1), (to', 1), (me', 1), (:', 1), (``', 1)]
  

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  条件频率分布

  当我们想要计算满足一组文本的特定条件的单词时，使用条件频率分布。

  
  import nltk
  #from nltk.tokenize import word_tokenize
  from nltk.corpus import brown
  cfd = nltk.ConditionalFreqDist(
            (genre, word)
            for genre in brown.categories()
            for word in brown.words(categories=genre))
  categories = ['hobbies', 'romance','humor']
  searchwords = [ 'may', 'might', 'must', 'will']
  cfd.tabulate(conditions=categories, samples=searchwords)
  

  当我们运行上述程序时，我们得到以下输出 -

  
            may might  must  will 
  hobbies   131    22    83   264 
  romance    11    51    45    43 
    humor     8     8     9    13