Simon Munzert, Christian Rubba, Peter Meißner, Dominic Nyhuis

Automated Data Collection with R (eBook, ePUB)

A Practical Guide to Web Scraping and Text Mining

• Format: ePub

Produktbeschreibung

A hands on guide to web scraping and text mining for both beginners and experienced users of R * Introduces fundamental concepts of the main architecture of the web and databases and covers HTTP, HTML, XML, JSON, SQL. * Provides basic techniques to query web documents and data sets (XPath and regular expressions). * An extensive set of exercises are presented to guide the reader through each technique. * Explores both supervised and unsupervised techniques as well as advanced techniques such as data scraping and text management. * Case studies are featured throughout along with examples for each technique presented. * R code and solutions to exercises featured in the book are provided on a supporting website.

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Produktdetails

• Verlag: John Wiley & Sons
• Seitenzahl: 480
• Erscheinungstermin: 18. Dezember 2014
• Englisch
• ISBN-13: 9781118834800
• Artikelnr.: 42045352

Autorenporträt

Simon Munzert is the author of Automated Data Collection with R: A Practical Guide to Web Scraping and Text Mining, published by Wiley. Christian Rubba is the author of Automated Data Collection with R: A Practical Guide to Web Scraping and Text Mining, published by Wiley. Peter Meißner is the author of Automated Data Collection with R: A Practical Guide to Web Scraping and Text Mining, published by Wiley. Dominic Nyhuis is the author of Automated Data Collection with R: A Practical Guide to Web Scraping and Text Mining, published by Wiley.

Inhaltsangabe

Preface xv 1 Introduction 1 1.1 Case study: World Heritage Sites in Danger
1 1.2 Some remarks on web data quality 7 1.3 Technologies for
disseminating, extracting, and storing web data 9 1.3.1 Technologies for
disseminating content on the Web 9 1.3.2 Technologies for information
extraction from web documents 11 1.3.3 Technologies for data storage 12 1.4
Structure of the book 13 Part One A Primer onWeb and Data Technologies 15 2
HTML 17 2.1 Browser presentation and source code 18 2.2 Syntax rules 19
2.2.1 Tags, elements, and attributes 20 2.2.2 Tree structure 21 2.2.3
Comments 22 2.2.4 Reserved and special characters 22 2.2.5 Document type
definition 23 2.2.6 Spaces and line breaks 23 2.3 Tags and attributes 24
2.3.1 The anchor tag 24 2.3.2 The metadata tag 25 2.3.3 The external
reference tag 26 2.3.4 Emphasizing tags , , 26 2.3.5 The paragraphs tag 27
2.3.6 Heading tags , , ,... 27 2.3.7 Listing content with , , and 27 2.3.8
The organizational tags and 27 2.3.9 The tag and its companions 29 2.3.10
The foreign script tag 30 2.3.11 Table tags , , , and 32 2.4 Parsing 32
2.4.1 What is parsing? 33 2.4.2 Discarding nodes 35 2.4.3 Extracting
information in the building process 37 Summary 38 Further reading 38
Problems 39 3 XML and JSON 41 3.1 A short example XML document 42 3.2 XML
syntax rules 43 3.2.1 Elements and attributes 44 3.2.2 XML structure 46
3.2.3 Naming and special characters 48 3.2.4 Comments and character data 49
3.2.5 XML syntax summary 50 3.3 When is an XML document well formed or
valid? 51 3.4 XML extensions and technologies 53 3.4.1 Namespaces 53 3.4.2
Extensions of XML 54 3.4.3 Example: Really Simple Syndication 55 3.4.4
Example: scalable vector graphics 58 3.5 XML and R in practice 60 3.5.1
Parsing XML 60 3.5.2 Basic operations on XML documents 63 3.5.3 From XML to
data frames or lists 65 3.5.4 Event-driven parsing 66 3.6 A short example
JSON document 68 3.7 JSON syntax rules 69 3.8 JSON and R in practice 71
Summary 76 Further reading 76 Problems 76 4 XPath 79 4.1 XPath--a query
language for web documents 80 4.2 Identifying node sets with XPath 81 4.2.1
Basic structure of an XPath query 81 4.2.2 Node relations 84 4.2.3 XPath
predicates 86 4.3 Extracting node elements 93 4.3.1 Extending the fun
argument 94 4.3.2 XML namespaces 96 4.3.3 Little XPath helper tools 97
Summary 98 Further reading 99 Problems 99 5 HTTP 101 5.1 HTTP fundamentals
102 5.1.1 A short conversation with a web server 102 5.1.2 URL syntax 104
5.1.3 HTTP messages 106 5.1.4 Request methods 108 5.1.5 Status codes 108
5.1.6 Header fields 109 5.2 Advanced features of HTTP 116 5.2.1
Identification 116 5.2.2 Authentication 121 5.2.3 Proxies 123 5.3 Protocols
beyond HTTP 124 5.3.1 HTTP Secure 124 5.3.2 FTP 126 5.4 HTTP in action 126
5.4.1 The libcurl library 127 5.4.2 Basic request methods 128 5.4.3 A
low-level function of RCurl 131 5.4.4 Maintaining connections across
multiple requests 132 5.4.5 Options 133 5.4.6 Debugging 139 5.4.7 Error
handling 143 5.4.8 RCurl or httr--what to use? 144 Summary 144 Further
reading 144 Problems 146 6 AJAX 149 6.1 JavaScript 150 6.1.1 How JavaScript
is used 150 6.1.2 DOM manipulation 151 6.2 XHR 154 6.2.1 Loading external
HTML/XML documents 155 6.2.2 Loading JSON 157 6.3 Exploring AJAX with Web
Developer Tools 158 6.3.1 Getting started with Chrome's Web Developer Tools
159 6.3.2 The Elements panel 159 6.3.3 The Network panel 160 Summary 161
Further reading 162 Problems 162 7 SQL and relational databases 164 7.1
Overview and terminology 165 7.2 Relational Databases 167 7.2.1 Storing
data in tables 167 7.2.2 Normalization 170 7.2.3 Advanced features of
relational databases and DBMS 174 7.3 SQL: a language to communicate with
Databases 175 7.3.1 General remarks on SQL, syntax, and our running example
175 7.3.2 Data control language--DCL 177 7.3.3 Data definition
language--DDL 178 7.3.4 Data manipulation language--DML 180 7.3.5 Clauses
184 7.3.6 Transaction control language--TCL 187 7.4 Databases in action 188
7.4.1 R packages to manage databases 188 7.4.2 Speaking R-SQL via DBI-based
packages 189 7.4.3 Speaking R-SQL via RODBC 191 Summary 192 Further reading
193 Problems 193 8 Regular expressions and essential string functions 196
8.1 Regular expressions 198 8.1.1 Exact character matching 198 8.1.2
Generalizing regular expressions 200 8.1.3 The introductory example
reconsidered 206 8.2 String processing 207 8.2.1 The stringr package 207
8.2.2 A couple more handy functions 211 8.3 A word on character encodings
214 Summary 216 Further reading 217 Problems 217 Part Two A Practical
Toolbox forWeb Scraping and Text Mining 219 9 Scraping the Web 221 9.1
Retrieval scenarios 222 9.1.1 Downloading ready-made files 223 9.1.2
Downloading multiple files from an FTP index 226 9.1.3 Manipulating URLs to
access multiple pages 228 9.1.4 Convenient functions to gather links,
lists, and tables from HTML documents 232 9.1.5 Dealing with HTML forms 235
9.1.6 HTTP authentication 245 9.1.7 Connections via HTTPS 246 9.1.8 Using
cookies 247 9.1.9 Scraping data from AJAX-enriched webpages with
Selenium/Rwebdriver 251 9.1.10 Retrieving data from APIs 259 9.1.11
Authentication with OAuth 266 9.2 Extraction strategies 270 9.2.1 Regular
expressions 270 9.2.2 XPath 273 9.2.3 Application Programming Interfaces
276 9.3 Web scraping: Good practice 278 9.3.1 Is web scraping legal? 278
9.3.2 What is robots.txt? 280 9.3.3 Be friendly! 284 9.4 Valuable sources
of inspiration 290 Summary 291 Further reading 292 Problems 293 10
Statistical text processing 295 10.1 The running example: Classifying press
releases of the British government 296 10.2 Processing textual data 298
10.2.1 Large-scale text operations--The tm package 298 10.2.2 Building a
term-document matrix 303 10.2.3 Data cleansing 304 10.2.4 Sparsity and
n-grams 305 10.3 Supervised learning techniques 307 10.3.1 Support vector
machines 309 10.3.2 Random Forest 309 10.3.3 Maximum entropy 309 10.3.4 The
RTextTools package 309 10.3.5 Application: Government press releases 310
10.4 Unsupervised learning techniques 313 10.4.1 Latent Dirichlet
Allocation and correlated topic models 314 10.4.2 Application: Government
press releases 314 Summary 320 Further reading 320 11 Managing data
projects 322 11.1 Interacting with the file system 322 11.2 Processing
multiple documents/links 323 11.2.1 Using for-loops 324 11.2.2 Using
while-loops and control structures 326 11.2.3 Using the plyr package 327
11.3 Organizing scraping procedures 328 11.3.1 Implementation of progress
feedback: Messages and progress bars 331 11.3.2 Error and exception
handling 333 11.4 Executing R scripts on a regular basis 334 11.4.1
Scheduling tasks on Mac OS and Linux 335 11.4.2 Scheduling tasks on Windows
platforms 337 Part Three A Bag of Case Studies 341 12 Collaboration
networks in the US Senate 343 12.1 Information on the bills 344 12.2
Information on the senators 350 12.3 Analyzing the network structure 353
12.3.1 Descriptive statistics 354 12.3.2 Network analysis 356 12.4
Conclusion 358 13 Parsing information from semistructured documents 359
13.1 Downloading data from the FTP server 360 13.2 Parsing semistructured
text data 361 13.3 Visualizing station and temperature data 368 14
Predicting the 2014 Academy Awards using Twitter 371 14.1 Twitter APIs:
Overview 372 14.1.1 The REST API 372 14.1.2 The Streaming APIs 373 14.1.3
Collecting and preparing the data 373 14.2 Twitter-based forecast of the
2014 Academy Awards 374 14.2.1 Visualizing the data 374 14.2.2 Mining
tweets for predictions 375 14.3 Conclusion 379 15 Mapping the geographic
distribution of names 380 15.1 Developing a data collection strategy 381
15.2 Website inspection 382 15.3 Data retrieval and information extraction
384 15.4 Mapping names 387 15.5 Automating the process 389 Summary 395 16
Gathering data on mobile phones 396 16.1 Page exploration 396 16.1.1
Searching mobile phones of a specific brand 396 16.1.2 Extracting product
information 400 16.2 Scraping procedure 404 16.2.1 Retrieving data on
several producers 404 16.2.2 Data cleansing 405 16.3 Graphical analysis 406
16.4 Data storage 408 16.4.1 General considerations 408 16.4.2 Table
definitions for storage 409 16.4.3 Table definitions for future storage 410
16.4.4 View definitions for convenient data access 411 16.4.5 Functions for
storing data 413 16.4.6 Data storage and inspection 415 17 Analyzing
sentiments of product reviews 416 17.1 Introduction 416 17.2 Collecting the
data 417 17.2.1 Downloading the files 417 17.2.2 Information extraction 421
17.2.3 Database storage 424 17.3 Analyzing the data 426 17.3.1 Data
preparation 426 17.3.2 Dictionary-based sentiment analysis 427 17.3.3
Mining the content of reviews 432 17.4 Conclusion 434 References 435
General index 442 Package index 448 Function index 449