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[SPARK-9680][MLlib][Doc] StopWordsRemovers user guide and Java compatibility test #8436
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@@ -306,15 +306,111 @@ regexTokenizer = RegexTokenizer(inputCol="sentence", outputCol="words", pattern= | |
</div> | ||
</div> | ||
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## StopWordsRemover | ||
[Stop words](https://en.wikipedia.org/wiki/Stop_words) are words which | ||
should be excluded from the input, typically because the words appear | ||
frequently and don't carry as much meaning. | ||
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`StopWordsRemover` takes as input a sequence of strings (e.g. the output | ||
of a [Tokenizer](ml-features.html#tokenizer)) and drops all the stop | ||
words from the input sequences. The list of stopwords is specified by | ||
the `stopWords` parameter. We provide [a list of stop | ||
words](http://ir.dcs.gla.ac.uk/resources/linguistic_utils/stop_words) by | ||
default, accessible by calling `getStopWords` on a newly instantiated | ||
`StopWordsRemover` instance. | ||
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## $n$-gram | ||
**Examples** | ||
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An [n-gram](https://en.wikipedia.org/wiki/N-gram) is a sequence of $n$ tokens (typically words) for some integer $n$. The `NGram` class can be used to transform input features into $n$-grams. | ||
Assume that we have the following DataFrame with columns `id` and `raw`: | ||
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`NGram` takes as input a sequence of strings (e.g. the output of a [Tokenizer](ml-features.html#tokenizer). The parameter `n` is used to determine the number of terms in each $n$-gram. The output will consist of a sequence of $n$-grams where each $n$-gram is represented by a space-delimited string of $n$ consecutive words. If the input sequence contains fewer than `n` strings, no output is produced. | ||
~~~~ | ||
id | raw | ||
----|---------- | ||
0 | [I, saw, the, red, baloon] | ||
1 | [Mary, had, a, little, lamb] | ||
~~~~ | ||
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Applying `StopWordsRemover` with `raw` as the input column and `filtered` as the output | ||
column, we should get the following: | ||
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~~~~ | ||
id | raw | filtered | ||
----|-----------------------------|-------------------- | ||
0 | [I, saw, the, red, baloon] | [saw, red, baloon] | ||
1 | [Mary, had, a, little, lamb]|[Mary, little, lamb] | ||
~~~~ | ||
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In `filtered`, the stop words "I", "the", "had", and "a" have been | ||
filtered out. | ||
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<div class="codetabs"> | ||
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<div data-lang="scala" markdown="1"> | ||
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[`StopWordsRemover`](api/scala/index.html#org.apache.spark.ml.feature.StopWordsRemover) | ||
takes an input column name, an output column name, a list of stop words, | ||
and a boolean indicating if the matches should be case sensitive (false | ||
by default). | ||
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{% highlight scala %} | ||
import org.apache.spark.ml.feature.StopWordsRemover | ||
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val remover = new StopWordsRemover() | ||
.setInputCol("raw") | ||
.setOutputCol("filtered") | ||
val dataSet = sqlContext.createDataFrame(Seq( | ||
(0, Seq("I", "saw", "the", "red", "baloon")), | ||
(1, Seq("Mary", "had", "a", "little", "lamb")) | ||
)).toDF("id", "raw") | ||
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remover.transform(dataSet).show() | ||
{% endhighlight %} | ||
</div> | ||
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<div data-lang="java" markdown="1"> | ||
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[`StopWordsRemover`](api/java/org/apache/spark/ml/feature/StopWordsRemover.html) | ||
takes an input column name, an output column name, a list of stop words, | ||
and a boolean indicating if the matches should be case sensitive (false | ||
by default). | ||
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{% highlight java %} | ||
import java.util.Arrays; | ||
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import org.apache.spark.api.java.JavaRDD; | ||
import org.apache.spark.ml.feature.StopWordsRemover; | ||
import org.apache.spark.sql.DataFrame; | ||
import org.apache.spark.sql.Row; | ||
import org.apache.spark.sql.RowFactory; | ||
import org.apache.spark.sql.types.DataTypes; | ||
import org.apache.spark.sql.types.Metadata; | ||
import org.apache.spark.sql.types.StructField; | ||
import org.apache.spark.sql.types.StructType; | ||
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StopWordsRemover remover = new StopWordsRemover() | ||
.setInputCol("raw") | ||
.setOutputCol("filtered"); | ||
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JavaRDD<Row> rdd = jsc.parallelize(Arrays.asList( | ||
RowFactory.create(Arrays.asList("I", "saw", "the", "red", "baloon")), | ||
RowFactory.create(Arrays.asList("Mary", "had", "a", "little", "lamb")) | ||
)); | ||
StructType schema = new StructType(new StructField[] { | ||
new StructField("raw", DataTypes.createArrayType(DataTypes.StringType), false, Metadata.empty()) | ||
}); | ||
DataFrame dataset = jsql.createDataFrame(rdd, schema); | ||
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remover.transform(dataset).show(); | ||
{% endhighlight %} | ||
</div> | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. TODO: add Python example There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Actually no Python example is possible until Python API is added (SPARK-9679, #8118); this TODO will be tracked by SPARK-10249 |
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</div> | ||
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## $n$-gram | ||
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An [n-gram](https://en.wikipedia.org/wiki/N-gram) is a sequence of $n$ tokens (typically words) for some integer $n$. The `NGram` class can be used to transform input features into $n$-grams. | ||
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`NGram` takes as input a sequence of strings (e.g. the output of a [Tokenizer](ml-features.html#tokenizer)). The parameter `n` is used to determine the number of terms in each $n$-gram. The output will consist of a sequence of $n$-grams where each $n$-gram is represented by a space-delimited string of $n$ consecutive words. If the input sequence contains fewer than `n` strings, no output is produced. | ||
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<div class="codetabs"> | ||
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<div data-lang="scala" markdown="1"> | ||
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/* | ||
* Licensed to the Apache Software Foundation (ASF) under one or more | ||
* contributor license agreements. See the NOTICE file distributed with | ||
* this work for additional information regarding copyright ownership. | ||
* The ASF licenses this file to You under the Apache License, Version 2.0 | ||
* (the "License"); you may not use this file except in compliance with | ||
* the License. You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
*/ | ||
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package org.apache.spark.ml.feature; | ||
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import java.util.Arrays; | ||
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import org.junit.After; | ||
import org.junit.Before; | ||
import org.junit.Test; | ||
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import org.apache.spark.api.java.JavaRDD; | ||
import org.apache.spark.api.java.JavaSparkContext; | ||
import org.apache.spark.sql.DataFrame; | ||
import org.apache.spark.sql.Row; | ||
import org.apache.spark.sql.RowFactory; | ||
import org.apache.spark.sql.SQLContext; | ||
import org.apache.spark.sql.types.DataTypes; | ||
import org.apache.spark.sql.types.Metadata; | ||
import org.apache.spark.sql.types.StructField; | ||
import org.apache.spark.sql.types.StructType; | ||
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public class JavaStopWordsRemoverSuite { | ||
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private transient JavaSparkContext jsc; | ||
private transient SQLContext jsql; | ||
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@Before | ||
public void setUp() { | ||
jsc = new JavaSparkContext("local", "JavaStopWordsRemoverSuite"); | ||
jsql = new SQLContext(jsc); | ||
} | ||
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@After | ||
public void tearDown() { | ||
jsc.stop(); | ||
jsc = null; | ||
} | ||
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@Test | ||
public void javaCompatibilityTest() { | ||
StopWordsRemover remover = new StopWordsRemover() | ||
.setInputCol("raw") | ||
.setOutputCol("filtered"); | ||
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JavaRDD<Row> rdd = jsc.parallelize(Arrays.asList( | ||
RowFactory.create(Arrays.asList("I", "saw", "the", "red", "baloon")), | ||
RowFactory.create(Arrays.asList("Mary", "had", "a", "little", "lamb")) | ||
)); | ||
StructType schema = new StructType(new StructField[] { | ||
new StructField("raw", DataTypes.createArrayType(DataTypes.StringType), false, Metadata.empty()) | ||
}); | ||
DataFrame dataset = jsql.createDataFrame(rdd, schema); | ||
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remover.transform(dataset).collect(); | ||
} | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. remover.fit? |
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} |
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It is useful to show the result, as in the user guide of
StringIndexer
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OK