使用spark的TF-IDF算法计算单词的重要性使用spark的TF-IDF算法计算单词的重要性

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使用spark的TF-IDF算法计算单词的重要性

本文简单学习一下spark的TF-IDF算法的使用

要计算每个单词的重要性，首先需要将单词分割，然后转换成数值型特征

In [1]:

from pyspark.ml.feature import HashingTF, IDF, Tokenizer
sentenceData = sqlContext.createDataFrame([
(0, "Hi I heard about Spark"),
(0, "I wish Java could use case classes"),
(1, "Logistic regression models are neat")
], ["label", "sentence"])
tokenizer = Tokenizer(inputCol="sentence", outputCol="words")
wordsData = tokenizer.transform(sentenceData)
wordsData.show(5, False)
hashingTF = HashingTF(inputCol="words", outputCol="rawFeatures", numFeatures=20)
featurizedData = hashingTF.transform(wordsData)
# alternatively, CountVectorizer can also be used to get term frequency vectors
featurizedData.select('rawFeatures', 'label').show(5, False)
idf = IDF(inputCol="rawFeatures", outputCol="features")
idfModel = idf.fit(featurizedData)
rescaledData = idfModel.transform(featurizedData)
rescaledData.select("features", "label").show(5, False)

+-----+-----------------------------------+------------------------------------------+
|label|sentence
|words
|
+-----+-----------------------------------+------------------------------------------+
|0
|Hi I heard about Spark
|[hi, i, heard, about, spark]
|
|0
|I wish Java could use case classes |[i, wish, java, could, use, case, classes]|
|1
|Logistic regression models are neat|[logistic, regression, models, are, neat] |
+-----+-----------------------------------+------------------------------------------+
+-----------------------------------------+-----+
|rawFeatures
|label|
+-----------------------------------------+-----+
|(20,[5,6,9],[2.0,1.0,2.0])
|0
|
|(20,[3,5,12,14,18],[2.0,2.0,1.0,1.0,1.0])|0
|
|(20,[5,12,14,18],[1.0,2.0,1.0,1.0])
|1
|
+-----------------------------------------+-----+
+--------------------------------------------------------------------------------------------------------+-----+
|features
|label|
+--------------------------------------------------------------------------------------------------------+-----+
|(20,[5,6,9],[0.0,0.6931471805599453,1.3862943611198906])
|0
|
|(20,[3,5,12,14,18],[1.3862943611198906,0.0,0.28768207245178085,0.28768207245178085,0.28768207245178085])|0
|
|(20,[5,12,14,18],[0.0,0.5753641449035617,0.28768207245178085,0.28768207245178085])
|1
|
+--------------------------------------------------------------------------------------------------------+-----+