主题分布：在python中执行LDA后，我们如何查看哪个文档属于哪个主题

Question

我能够运行gensim的LDA代码，并获得各自关键词的前10个主题。

现在，我想更进一步，通过查看将哪些文档归类到每个主题中，来了解LDA算法的准确性。gensim LDA有可能吗？

基本上我想做这样的事情，但是在python中并使用gensim。

具有主题模型的LDA，如何查看不同文档属于哪些主题？

Answer 1

使用主题的概率，您可以尝试设置一些阈值并将其用作聚类基线，但是我敢肯定，比这种“ hacky”方法有更好的聚类方法。

    from gensim import corpora, models, similarities
    from itertools import chain

    """ DEMO """
    documents = ["Human machine interface for lab abc computer applications",
                 "A survey of user opinion of computer system response time",
                 "The EPS user interface management system",
                 "System and human system engineering testing of EPS",
                 "Relation of user perceived response time to error measurement",
                 "The generation of random binary unordered trees",
                 "The intersection graph of paths in trees",
                 "Graph minors IV Widths of trees and well quasi ordering",
                 "Graph minors A survey"]

    # remove common words and tokenize
    stoplist = set('for a of the and to in'.split())
    texts = [[word for word in document.lower().split() if word not in stoplist]
             for document in documents]

    # remove words that appear only once
    all_tokens = sum(texts, [])
    tokens_once = set(word for word in set(all_tokens) if all_tokens.count(word) == 1)
    texts = [[word for word in text if word not in tokens_once] for text in texts]

    # Create Dictionary.
    id2word = corpora.Dictionary(texts)
    # Creates the Bag of Word corpus.
    mm = [id2word.doc2bow(text) for text in texts]

    # Trains the LDA models.
    lda = models.ldamodel.LdaModel(corpus=mm, id2word=id2word, num_topics=3, \
                                   update_every=1, chunksize=10000, passes=1)

    # Prints the topics.
    for top in lda.print_topics():
      print top
    print

    # Assigns the topics to the documents in corpus
    lda_corpus = lda[mm]

    # Find the threshold, let's set the threshold to be 1/#clusters,
    # To prove that the threshold is sane, we average the sum of all probabilities:
    scores = list(chain(*[[score for topic_id,score in topic] \
                          for topic in [doc for doc in lda_corpus]]))
    threshold = sum(scores)/len(scores)
    print threshold
    print

    cluster1 = [j for i,j in zip(lda_corpus,documents) if i[0][1] > threshold]
    cluster2 = [j for i,j in zip(lda_corpus,documents) if i[1][1] > threshold]
    cluster3 = [j for i,j in zip(lda_corpus,documents) if i[2][1] > threshold]

    print cluster1
    print cluster2
    print cluster3

[out]：

    0.131*trees + 0.121*graph + 0.119*system + 0.115*user + 0.098*survey + 0.082*interface + 0.080*eps + 0.064*minors + 0.056*response + 0.056*computer
    0.171*time + 0.171*user + 0.170*response + 0.082*survey + 0.080*computer + 0.079*system + 0.050*trees + 0.042*graph + 0.040*minors + 0.040*human
    0.155*system + 0.150*human + 0.110*graph + 0.107*minors + 0.094*trees + 0.090*eps + 0.088*computer + 0.087*interface + 0.040*survey + 0.028*user

    0.333333333333

    ['The EPS user interface management system', 'The generation of random binary unordered trees', 'The intersection graph of paths in trees', 'Graph minors A survey']
    ['A survey of user opinion of computer system response time', 'Relation of user perceived response time to error measurement']
    ['Human machine interface for lab abc computer applications', 'System and human system engineering testing of EPS', 'Graph minors IV Widths of trees and well quasi ordering']

为了更清楚一点：

    # Find the threshold, let's set the threshold to be 1/#clusters,
    # To prove that the threshold is sane, we average the sum of all probabilities:
    scores = []
    for doc in lda_corpus
        for topic in doc:
            for topic_id, score in topic:
                scores.append(score)
    threshold = sum(scores)/len(scores)

上面的代码是所有单词和所有主题的所有主题的总分。然后通过分数的数量归一化总和。