cavis/docs/datavec/templates/analysis.md

title	short_title	description	category	weight
DataVec Analysis	Analysis	Gather statistics on datasets.	DataVec	2

Analysis of data

Sometimes datasets are too large or too abstract in their format to manually analyze and estimate statistics on certain columns or patterns. DataVec comes with some helper utilities for performing a data analysis, and maximums, means, minimums, and other useful metrics.

Using Spark for analysis

If you have loaded your data into Apache Spark, DataVec has a special AnalyzeSpark class which can generate histograms, collect statistics, and return information about the quality of the data. Assuming you have already loaded your data into a Spark RDD, pass the JavaRDD and Schema to the class.

If you are using DataVec in Scala and your data was loaded into a regular RDD class, you can convert it by calling .toJavaRDD() which returns a JavaRDD. If you need to convert it back, call rdd().

The code below demonstrates some of many analyses for a 2D dataset in Spark analysis using the RDD javaRdd and the schema mySchema:

import org.datavec.spark.transform.AnalyzeSpark;
import org.datavec.api.writable.Writable;
import org.datavec.api.transform.analysis.*;

int maxHistogramBuckets = 10
DataAnalysis analysis = AnalyzeSpark.analyze(mySchema, javaRdd, maxHistogramBuckets)

DataQualityAnalysis analysis = AnalyzeSpark.analyzeQuality(mySchema, javaRdd)

Writable max = AnalyzeSpark.max(javaRdd, "myColumn", mySchema)

int numSamples = 5
List<Writable> sample = AnalyzeSpark.sampleFromColumn(numSamples, "myColumn", mySchema, javaRdd)

Note that if you have sequence data, there are special methods for that as well:

SequenceDataAnalysis seqAnalysis = AnalyzeSpark.analyzeSequence(mySchema, sequenceRdd)

List<Writable> uniqueSequence = AnalyzeSpark.getUniqueSequence("myColumn", seqSchema, sequenceRdd)

Analyzing locally

The AnalyzeLocal class works very similarly to its Spark counterpart and has a similar API. Instead of passing an RDD, it accepts a RecordReader which allows it to iterate over the dataset.

import org.datavec.local.transforms.AnalyzeLocal;

int maxHistogramBuckets = 10
DataAnalysis analysis = AnalyzeLocal.analyze(mySchema, csvRecordReader, maxHistogramBuckets)

Utilities

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