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Diffstat (limited to 'docs/mllib-naive-bayes.md')
| -rw-r--r-- | docs/mllib-naive-bayes.md | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/docs/mllib-naive-bayes.md b/docs/mllib-naive-bayes.md index a83472f5be..9780ea52c4 100644 --- a/docs/mllib-naive-bayes.md +++ b/docs/mllib-naive-bayes.md @@ -13,12 +13,15 @@ compute the conditional probability distribution of label given an observation and use it for prediction. MLlib supports [multinomial naive -Bayes](http://en.wikipedia.org/wiki/Naive_Bayes_classifier#Multinomial_naive_Bayes), -which is typically used for [document -classification](http://nlp.stanford.edu/IR-book/html/htmledition/naive-bayes-text-classification-1.html). +Bayes](http://en.wikipedia.org/wiki/Naive_Bayes_classifier#Multinomial_naive_Bayes) +and [Bernoulli naive Bayes] (http://nlp.stanford.edu/IR-book/html/htmledition/the-bernoulli-model-1.html). +These models are typically used for [document classification] +(http://nlp.stanford.edu/IR-book/html/htmledition/naive-bayes-text-classification-1.html). Within that context, each observation is a document and each -feature represents a term whose value is the frequency of the term. -Feature values must be nonnegative to represent term frequencies. +feature represents a term whose value is the frequency of the term (in multinomial naive Bayes) or +a zero or one indicating whether the term was found in the document (in Bernoulli naive Bayes). +Feature values must be nonnegative. The model type is selected with an optional parameter +"Multinomial" or "Bernoulli" with "Multinomial" as the default. [Additive smoothing](http://en.wikipedia.org/wiki/Lidstone_smoothing) can be used by setting the parameter $\lambda$ (default to $1.0$). For document classification, the input feature vectors are usually sparse, and sparse vectors should be supplied as input to take advantage of @@ -32,7 +35,7 @@ sparsity. Since the training data is only used once, it is not necessary to cach [NaiveBayes](api/scala/index.html#org.apache.spark.mllib.classification.NaiveBayes$) implements multinomial naive Bayes. It takes an RDD of [LabeledPoint](api/scala/index.html#org.apache.spark.mllib.regression.LabeledPoint) and an optional -smoothing parameter `lambda` as input, and output a +smoothing parameter `lambda` as input, an optional model type parameter (default is Multinomial), and outputs a [NaiveBayesModel](api/scala/index.html#org.apache.spark.mllib.classification.NaiveBayesModel), which can be used for evaluation and prediction. @@ -51,7 +54,7 @@ val splits = parsedData.randomSplit(Array(0.6, 0.4), seed = 11L) val training = splits(0) val test = splits(1) -val model = NaiveBayes.train(training, lambda = 1.0) +val model = NaiveBayes.train(training, lambda = 1.0, model = "Multinomial") val predictionAndLabel = test.map(p => (model.predict(p.features), p.label)) val accuracy = 1.0 * predictionAndLabel.filter(x => x._1 == x._2).count() / test.count() |