book

Practical Time Series Analysis

by Aileen Nielsen

October 2019

Beginner to intermediate

497 pages

14h

English

O'Reilly Media, Inc.

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Who Should Read This BookExpected BackgroundWhy I Wrote This BookNavigating This BookOnline ResourcesConventions Used in This BookUsing Code ExamplesO’Reilly Online LearningHow to Contact UsAcknowledgments
The History of Time Series in Diverse ApplicationsMedicine as a Time Series ProblemForecasting WeatherForecasting Economic GrowthAstronomyTime Series Analysis Takes OffThe Origins of Statistical Time Series AnalysisThe Origins of Machine Learning Time Series AnalysisMore Resources
Where to Find Time Series DataPrepared Data SetsFound Time SeriesRetrofitting a Time Series Data Collection from a Collection of TablesA Worked Example: Assembling a Time Series Data CollectionConstructing a Found Time SeriesTimestamping TroublesWhose Timestamp?Guesstimating Timestamps to Make Sense of DataWhat’s a Meaningful Time Scale?Cleaning Your DataHandling Missing DataUpsampling and DownsamplingSmoothing DataSeasonal DataTime ZonesPreventing LookaheadMore Resources
Familiar MethodsPlottingHistogramsScatter PlotsTime Series–Specific Exploratory MethodsUnderstanding StationarityApplying Window FunctionsUnderstanding and Identifying Self-CorrelationSpurious CorrelationsSome Useful Visualizations1D Visualizations2D Visualizations3D VisualizationsMore Resources
What’s Special About Simulating Time Series?Simulation Versus ForecastingSimulations in CodeDoing the Work YourselfBuilding a Simulation Universe That Runs ItselfA Physics SimulationFinal Notes on SimulationsStatistical SimulationsDeep Learning SimulationsMore Resources
Defining RequirementsLive Data Versus Stored DataDatabase SolutionsSQL Versus NoSQLPopular Time Series Database and File SolutionsFile SolutionsNumPyPandasStandard R EquivalentsXarrayMore Resources
Why Not Use a Linear Regression?Statistical Methods Developed for Time SeriesAutoregressive ModelsMoving Average ModelsAutoregressive Integrated Moving Average ModelsVector AutoregressionVariations on Statistical ModelsAdvantages and Disadvantages of Statistical Methods for Time SeriesMore Resources
State Space Models: Pluses and MinusesThe Kalman FilterOverviewCode for the Kalman FilterHidden Markov ModelsHow the Model WorksHow We Fit the ModelFitting an HMM in CodeBayesian Structural Time SeriesCode for bstsMore Resources
Introductory ExampleGeneral Considerations When Computing FeaturesThe Nature of the Time SeriesDomain KnowledgeExternal ConsiderationsA Catalog of Places to Find Features for InspirationOpen Source Time Series Feature Generation LibrariesDomain-Specific Feature ExamplesHow to Select Features Once You Have Generated ThemConcluding ThoughtsMore Resources
Time Series ClassificationSelecting and Generating FeaturesDecision Tree MethodsClusteringGenerating Features from the DataTemporally Aware Distance MetricsClustering CodeMore Resources

Deep Learning ConceptsProgramming a Neural NetworkData, Symbols, Operations, Layers, and GraphsBuilding a Training PipelineInspecting Our Data SetSteps of a Training PipelineFeed Forward NetworksA Simple ExampleUsing an Attention Mechanism to Make Feed Forward Networks More Time-AwareCNNsA Simple Convolutional ModelAlternative Convolutional ModelsRNNsContinuing Our Electric ExampleThe Autoencoder InnovationCombination ArchitecturesSumming UpMore Resources
The Basics: How to Test ForecastsModel-Specific Considerations for BacktestingWhen Is Your Forecast Good Enough?Estimating Uncertainty in Your Model with a SimulationPredicting Multiple Steps AheadFit Directly to the Horizon of InterestRecursive Approach to Distant Temporal HorizonsMultitask Learning Applied to Time SeriesModel Validation GotchasMore Resources
Working with Tools Built for More General Use CasesModels Built for Cross-Sectional Data Don’t “Share” Data Across SamplesModels That Don’t Precompute Create Unnecessary Lag Between Measuring Data and Making a ForecastData Storage Formats: Pluses and MinusesStore Your Data in a Binary FormatPreprocess Your Data in a Way That Allows You to “Slide” Over ItModifying Your Analysis to Suit Performance ConsiderationsUsing All Your Data Is Not Necessarily BetterComplicated Models Don’t Always Do Better EnoughA Brief Mention of Alternative High-Performance ToolsMore Resources
Predicting the FluA Case Study of Flu in One Metropolitan AreaWhat Is State of the Art in Flu Forecasting?Predicting Blood Glucose LevelsData Cleaning and ExplorationGenerating FeaturesFitting a ModelMore Resources
Obtaining and Exploring Financial DataPreprocessing Financial Data for Deep LearningAdding Quantities of Interest to Our Raw ValuesScaling Quantities of Interest Without a LookaheadFormatting Our Data for a Neural NetworkBuilding and Training an RNNMore Resources
Obtaining Governmental DataExploring Big Time Series DataUpsample and Aggregate the Data as We Iterate Through ItSort the DataOnline Statistical Analysis of Time Series DataRemaining QuestionsFurther ImprovementsMore Resources
Forecasting at ScaleGoogle’s Industrial In-house ForecastingFacebook’s Open Source Prophet PackageAnomaly DetectionTwitter’s Open Source AnomalyDetection PackageOther Time Series PackagesMore Resources
Forecasting as a ServiceDeep Learning Enhances Probabilistic PossibilitiesIncreasing Importance of Machine Learning Rather Than StatisticsIncreasing Combination of Statistical and Machine Learning MethodologiesMore Forecasts for Everyday Life

Content preview from Practical Time Series Analysis

Chapter 5. Storing Temporal Data

Often, the value of time series data comes in its retrospective, rather than live streaming, scenarios. For this reason, storage of time series data is necessary for most time series analysis.

A good storage solution is one that enables ease of access and reliability of data without requiring a major investment of computing resources. In this chapter, we will discuss what aspects of a data set you should consider when designing for time series data storage. We will also discuss the advantages of SQL databases, NoSQL databases, and a variety of flat file formats.

Designing a general time series storage solution is a challenge because there are so many different kinds of time series data, each with different storage, read/write, and analysis patterns. Some data will be stored and examined repeatedly, whereas other data is useful only for a short period of time, after which it can be deleted altogether.

Here are a few use cases for time series storage that have different read, write, and query patterns:

You are collecting performance metrics on a production system. You need to store these performance metrics for years at a time, but the older the data gets, the less detailed it needs to be. Hence you need a form of storage that will automatically downsample and cull data as information ages.
You have access to a remote open source time series data repository, but you need to keep a local copy on your computer to cut down on network traffic. The ...