hop-user-manual/modules/ROOT/pages/plugins/transforms/reservoirsampling.adoc - incubator-hop-docs - Git at Google

 ////
 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.
 ////
 :documentationPath: /plugins/transforms/
 :language: en_US
 :page-alternativeEditUrl: https://github.com/apache/incubator-hop/edit/master/plugins/transforms/reservoirsampling/src/main/doc/reservoirsampling.adoc

 = Reservoir Sampling

 == Description

 The Reservoir Sampling transform allows you to sample a fixed number of rows from an incoming data stream when the total number of incoming rows is not known in advance. The transform uses uniform sampling; all incoming rows have an equal chance of being selected. This transform is particularly useful when used in conjunction with the ARFF output transform in order to generate a suitable sized data set to be used by WEKA. The reservoir sampling transform uses link:https://en.wikipedia.org/wiki/Reservoir_sampling[Algorithm R] by Jeffery Vitter.

 == Options

 [width="90%", options="header"]
 |===
 |Option|Description
 |Transform name|Name of the transform this name has to be unique in a single pipeline.
 |Sample size|Select how many rows to sample from an incoming stream. Setting a value of 0 will cause all rows to be sampled; setting a negative value will block all rows.
 |Random seed|Choose a seed for the random number generator. Repeating a pipeline with a different value for the seed will result in a different random sample being chosen.
 |===
	////
	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.
	////
	:documentationPath: /plugins/transforms/
	:language: en_US
	:page-alternativeEditUrl: https://github.com/apache/incubator-hop/edit/master/plugins/transforms/reservoirsampling/src/main/doc/reservoirsampling.adoc

	= Reservoir Sampling

	== Description

	The Reservoir Sampling transform allows you to sample a fixed number of rows from an incoming data stream when the total number of incoming rows is not known in advance. The transform uses uniform sampling; all incoming rows have an equal chance of being selected. This transform is particularly useful when used in conjunction with the ARFF output transform in order to generate a suitable sized data set to be used by WEKA. The reservoir sampling transform uses link:https://en.wikipedia.org/wiki/Reservoir_sampling[Algorithm R] by Jeffery Vitter.

	== Options

	[width="90%", options="header"]
	\|===
	\|Option\|Description
	\|Transform name\|Name of the transform this name has to be unique in a single pipeline.
	\|Sample size\|Select how many rows to sample from an incoming stream. Setting a value of 0 will cause all rows to be sampled; setting a negative value will block all rows.
	\|Random seed\|Choose a seed for the random number generator. Repeating a pipeline with a different value for the seed will result in a different random sample being chosen.
	\|===