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2013-02-01-Obtaining-Data.html
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2013-02-01-Obtaining-Data.html
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<title>2013-02-01-Obtaining-Data</title>
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</head>
<body>
<div id="preamble">
</div>
<div id="content">
<h1 class="title">2013-02-01-Obtaining-Data</h1>
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#sec-1">1 Obtaining Data</a></li>
<li><a href="#sec-2">2 Ways to Collect</a>
<ul>
<li><a href="#sec-2-1">2.1 Operational Data</a>
<ul>
<li><a href="#sec-2-1-1">2.1.1 Data from production</a></li>
</ul>
</li>
<li><a href="#sec-2-2">2.2 Example</a>
<ul>
<li><a href="#sec-2-2-1">2.2.1 Distributed Data</a></li>
</ul>
</li>
<li><a href="#sec-2-3">2.3 Data Warehouse</a>
<ul>
<li><a href="#sec-2-3-1">2.3.1 No free lunch</a></li>
</ul>
</li>
<li><a href="#sec-2-4">2.4 Unstructured</a>
<ul>
<li><a href="#sec-2-4-1">2.4.1 Yelp JSON logs</a></li>
</ul>
</li>
<li><a href="#sec-2-5">2.5 Search Logs Example</a>
<ul>
<li><a href="#sec-2-5-1">2.5.1 Imposing Structure</a></li>
</ul>
</li>
<li><a href="#sec-2-6">2.6 External APIs</a>
<ul>
<li><a href="#sec-2-6-1">2.6.1 Motivation</a></li>
</ul>
</li>
<li><a href="#sec-2-7">2.7 NYTimes API Example</a>
<ul>
<li><a href="#sec-2-7-1">2.7.1 Accessing these</a></li>
</ul>
</li>
<li><a href="#sec-2-8">2.8 Data Sets</a>
<ul>
<li><a href="#sec-2-8-1">2.8.1 Research</a></li>
</ul>
</li>
<li><a href="#sec-2-9">2.9 Data Set Example</a></li>
</ul>
</li>
<li><a href="#sec-3">3 Exploring Data</a>
<ul>
<li><a href="#sec-3-1">3.1 Size</a></li>
</ul>
</li>
<li><a href="#sec-4">4 Yelp Academic Dataset</a>
<ul>
<li><a href="#sec-4-1">4.1 Example</a></li>
</ul>
</li>
<li><a href="#sec-5">5 CLI introduction</a>
<ul>
<li><a href="#sec-5-1">5.1 Help</a></li>
</ul>
</li>
<li><a href="#sec-6">6 <code>wget</code></a>
<ul>
<li><a href="#sec-6-1">6.1 Command</a></li>
</ul>
</li>
<li><a href="#sec-7">7 <code>scp</code></a>
<ul>
<li><a href="#sec-7-1">7.1 Command</a></li>
</ul>
</li>
<li><a href="#sec-8">8 <code>gunzip</code> <code>unzip</code></a>
<ul>
<li><a href="#sec-8-1">8.1 Commands</a></li>
</ul>
</li>
<li><a href="#sec-9">9 <code>less</code></a></li>
<li><a href="#sec-10">10 Searching in <code>less</code></a>
<ul>
<li><a href="#sec-10-1">10.1 Command</a></li>
</ul>
</li>
<li><a href="#sec-11">11 <code>grep</code></a></li>
<li><a href="#sec-12">12 <code>wc</code></a></li>
<li><a href="#sec-13">13 Composable</a></li>
</ul>
</div>
</div>
<div id="outline-container-1" class="outline-2">
<h2 id="sec-1"><span class="section-number-2">1</span> Obtaining Data <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-1">
</div>
</div>
<div id="outline-container-2" class="outline-2">
<h2 id="sec-2"><span class="section-number-2">2</span> Ways to Collect <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-2">
<ul>
<li>Operational Data
</li>
<li>Data Warehouse
</li>
<li>Unstructured Data
</li>
<li>External API
</li>
<li>Data Sets
</li>
</ul>
<p>
<img src="img/bottlecaps.jpg" alt="img/bottlecaps.jpg" />
</p>
</div>
<div id="outline-container-2-1" class="outline-3">
<h3 id="sec-2-1"><span class="section-number-3">2.1</span> Operational Data <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-1">
<ul>
<li>Most frequent in industry
</li>
<li>Usually stored in databases best suited for transactional use
</li>
<li>Challenge is reorganizing data to suit question
</li>
</ul>
</div>
<div id="outline-container-2-1-1" class="outline-4">
<h4 id="sec-2-1-1"><span class="section-number-4">2.1.1</span> Data from production <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-1-1">
<ul>
<li>Most frequently you'll have data that is being used by the application,
and you'll want to find insights in it
</li>
<li>We'll go into more detail in another class, but online use is
optimized for small queries and small updates
</li>
<li>Frequently just accessing the data in bulk is a software engineering
problem:
<ul>
<li>ensuring long queries don't hold up production usage
</li>
<li>joining across databases via software
</li>
<li>understanding esoteric columns, like "flags"
</li>
</ul>
</li>
<li>Often will want to reorganize data to look like transactional
</li>
<li>img: <a href="http://woodwarddesign.ca/blog/2009/03/06/bottle-caps/">http://woodwarddesign.ca/blog/2009/03/06/bottle-caps/</a>
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-2" class="outline-3">
<h3 id="sec-2-2"><span class="section-number-3">2.2</span> Example <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-2">
<ul>
<li>Find the user names with most "liked" reviews on Yelp
</li>
</ul>
<p>
users
</p><table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<caption></caption>
<colgroup><col class="left" /><col class="left" /><col class="left" />
</colgroup>
<tbody>
<tr><td class="left">userID</td><td class="left">name</td><td class="left">flags</td></tr>
<tr><td class="left">25234</td><td class="left">Jim</td><td class="left">0x200</td></tr>
</tbody>
</table>
<p>
reviews
</p><table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<caption></caption>
<colgroup><col class="left" /><col class="left" /><col class="left" /><col class="left" /><col class="left" /><col class="left" />
</colgroup>
<tbody>
<tr><td class="left">reviewID</td><td class="left">businessID</td><td class="left">userID</td><td class="left">stars</td><td class="left">text</td><td class="left">flags</td></tr>
<tr><td class="left">282</td><td class="left">52432</td><td class="left">25234</td><td class="left">4</td><td class="left">great place!</td><td class="left">0x1</td></tr>
</tbody>
</table>
<p>
feedback
</p><table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<caption></caption>
<colgroup><col class="left" /><col class="left" /><col class="left" /><col class="left" />
</colgroup>
<tbody>
<tr><td class="left">reviewID</td><td class="left">srcUserID</td><td class="left">ufcFlags</td><td class="left">flags</td></tr>
<tr><td class="left">282</td><td class="left">8205</td><td class="left">0x1</td><td class="left">0x0</td></tr>
</tbody>
</table>
</div>
<div id="outline-container-2-2-1" class="outline-4">
<h4 id="sec-2-2-1"><span class="section-number-4">2.2.1</span> Distributed Data <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-2-1">
<ul>
<li>At Yelp we have a variety of database tables, and those tables can be
spread across different databases
</li>
<li>At a minimum we frequently need to <code>JOIN</code> across tables to answer queries
<ul>
<li>eg. matching up user names with reviews from separate tables
</li>
</ul>
</li>
<li>It is possible the review table is only indexed on business ID, and so
finding all reviews by a user is really disk intensive: make sure you're
not slowing down the whole site!
</li>
<li>An additional challenge is when the "feedback" tables are in a separate
database: can no longer issue normal SQL queries
</li>
<li>What are these "flag" columns for?
</li>
<li>Exactly: no one knows. Often must look into code, or compare data to
production representation to guess meaning. In Yelp, <code>0x1</code> often means
"inactive", so we probably don't want to count that feedback
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-3" class="outline-3">
<h3 id="sec-2-3"><span class="section-number-3">2.3</span> Data Warehouse <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h3>
<div class="outline-text-3" id="text-2-3">
<ul>
<li>Data located on same system
</li>
<li>Organized for analytics queries
</li>
<li>Requires extra maintenance and understanding of construction
</li>
</ul>
<p>
<img src="img/Ikea-Warehouse.jpg" alt="img/Ikea-Warehouse.jpg" />
</p>
</div>
<div id="outline-container-2-3-1" class="outline-4">
<h4 id="sec-2-3-1"><span class="section-number-4">2.3.1</span> No free lunch <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-3-1">
<ul>
<li>A strong data warehouse can be a big improvement over operational data
</li>
<li>Hopefully, someone has already cleaned, joined data in a way that makes
sense!
</li>
<li>Optimized for long running queries: less fear of brining down website!
</li>
<li>But you must learn how that process was accomplished in order to understand
potential problems
</li>
<li>How to handle missing data?
</li>
<li>We'll go into more detail about how data warehouse schemas compare to
online ones later in the course
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-4" class="outline-3">
<h3 id="sec-2-4"><span class="section-number-3">2.4</span> Unstructured <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-4">
<ul>
<li>Haphazard collection of data
</li>
<li>Unclear what structure should be
</li>
<li>Examples: Web logs, text, multimedia
</li>
<li>Must extract structure eventually
</li>
</ul>
</div>
<div id="outline-container-2-4-1" class="outline-4">
<h4 id="sec-2-4-1"><span class="section-number-4">2.4.1</span> Yelp JSON logs <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-4-1">
<ul>
<li>When developing a web application, new context or details become
important: how long did certain requests take? What link did a user follow
to a website?
</li>
<li>Relational Databases aren't well suited for these wide varieties of
potential attributes that don't apply to all items
</li>
<li>So the current work around is just to write all useful information down in
a log, and extract what is needed later
</li>
<li>Text, like business reviews, another example: desired structure changes
radically between questions: How many words? Characters? What is the sentiment?
</li>
<li>Pictures can contain attributes like color depth, length, width
</li>
<li>First step of data mining is often imposing structure on data: the data is
not inherently unstructured, it just is unclear what the structure <b>should be</b>
until query time
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-5" class="outline-3">
<h3 id="sec-2-5"><span class="section-number-3">2.5</span> Search Logs Example <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-5">
<pre class="src src-log">193.139.1 jim [10/Oct/2013:13:55:36 -0700] <span style="color: #8b2252;">"GET /search?query=headache HTTP/1.1"</span> 200 9288
282.482.3 shreyas [10/Oct/2013:13:56:36 -0700] <span style="color: #8b2252;">"GET /search?query=bananas HTTP/1.1"</span> 200 2929
345.114.1 steven [10/Oct/2013:13:56:37 -0700] <span style="color: #8b2252;">"GET /search?query=cold HTTP/1.1"</span> 200 8232
10.328.52 anne [10/Oct/2013:13:56:39 -0700] <span style="color: #8b2252;">"GET /search?query=flu+shot HTTP/1.1"</span> 200 2342
10.328.52 lily [10/Oct/2013:13:57:40 -0700] <span style="color: #8b2252;">"GET /search?query=i290 HTTP/1.1"</span> 200 2342
</pre>
<table border="2" cellspacing="0" cellpadding="6" rules="groups" frame="hsides">
<caption></caption>
<colgroup><col class="left" /><col class="left" /><col class="left" />
</colgroup>
<tbody>
<tr><td class="left">userName</td><td class="left">date</td><td class="left">query</td></tr>
<tr><td class="left">jim</td><td class="left">10/Oct/2013:13:55:36 -0700</td><td class="left">headache</td></tr>
<tr><td class="left">shreyas</td><td class="left">10/Oct/2013:13:56:36 -0700</td><td class="left">bananas</td></tr>
<tr><td class="left">steven</td><td class="left">10/Oct/2013:13:56:37 -0700</td><td class="left">cold</td></tr>
<tr><td class="left">anne</td><td class="left">10/Oct/2013:13:56:39 -0700</td><td class="left">flu shot</td></tr>
<tr><td class="left">lily</td><td class="left">10/Oct/2013:13:57:40 -0700</td><td class="left">i290</td></tr>
</tbody>
</table>
</div>
<div id="outline-container-2-5-1" class="outline-4">
<h4 id="sec-2-5-1"><span class="section-number-4">2.5.1</span> Imposing Structure <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-5-1">
<ul>
<li>Extract only the rows we know follow a format
</li>
<li>Format queries from some encoding (eg. URL) to standardized format
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-6" class="outline-3">
<h3 id="sec-2-6"><span class="section-number-3">2.6</span> External APIs <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-6">
<ul>
<li>Better documented than internal data!
</li>
<li>More limited in amount and detail
</li>
<li>Commonly HTTP/REST based
</li>
</ul>
</div>
<div id="outline-container-2-6-1" class="outline-4">
<h4 id="sec-2-6-1"><span class="section-number-4">2.6.1</span> Motivation <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-6-1">
<ul>
<li>Companies are often searching for other ways to leverage their data
</li>
<li>Both for immediate business purposes, and for brand recognition
</li>
<li>Twitter more (in)famous example
</li>
<li>NYTimes another good option
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-7" class="outline-3">
<h3 id="sec-2-7"><span class="section-number-3">2.7</span> NYTimes API Example <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-7">
<ul>
<li><a href="http://developer.nytimes.com/docs/read/article_search_api">Article Search API</a>
</li>
<li><a href="http://api.nytimes.com/svc/search/v1/article?format=json&query=ballot&api-key=6578bab7f8c3808ce4c392edc9a793f0:8:5717915">http://api.nytimes.com/svc/search/v1/article?format=json&query=ballot&api-key=6578bab7f8c3808ce4c392edc9a793f0:8:5717915</a>
</li>
</ul>
</div>
<div id="outline-container-2-7-1" class="outline-4">
<h4 id="sec-2-7-1"><span class="section-number-4">2.7.1</span> Accessing these <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-7-1">
<ul>
<li>More info on how to access these APIs is in the Web Architecture class,
but feel free to ask Shreyas or I about how best to access them
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-8" class="outline-3">
<h3 id="sec-2-8"><span class="section-number-3">2.8</span> Data Sets <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-2-8">
<ul>
<li>Download large, curated set of data all at once
</li>
<li>Formats vary, but usually documented
</li>
<li>Can be useful to combine with other datasets or APIs
</li>
</ul>
<p>
<img src="img/kaggle-digits.png" alt="img/kaggle-digits.png" />
</p>
</div>
<div id="outline-container-2-8-1" class="outline-4">
<h4 id="sec-2-8-1"><span class="section-number-4">2.8.1</span> Research <span class="tag"><span class="notes">notes</span></span></h4>
<div class="outline-text-4" id="text-2-8-1">
<ul>
<li>Data sets commonly used in research: can compare different techniques on
same data to understand advantages
</li>
<li>Sizes can range to a few MB to GB
</li>
<li>JSON, CSV, XML all potential formats. Cleaning, organization for your
question again becomes an important aspect
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-2-9" class="outline-3">
<h3 id="sec-2-9"><span class="section-number-3">2.9</span> Data Set Example <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h3>
<div class="outline-text-3" id="text-2-9">
<ul>
<li><a href="http://www.grouplens.org/node/73">MovieLens Data Sets</a>
</li>
<li><a href="https://www.kaggle.com/c/digit-recognizer">Kaggle Digit Recognizer</a>
</li>
<li><a href="https://bitly.com/bundles/hmason/1">Hilary Mason's Data Sets</a>
</li>
</ul>
<p>
<img src="img/video.jpg" alt="img/video.jpg" />
</p>
</div>
</div>
</div>
<div id="outline-container-3" class="outline-2">
<h2 id="sec-3"><span class="section-number-2">3</span> Exploring Data <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-3">
<ul>
<li>Data sets are frequently too large to fit in standard tools like Excel or
Word
</li>
<li>Simplest to explore on the command line
</li>
<li>Homework will be exploring a data set of your choice
</li>
</ul>
</div>
<div id="outline-container-3-1" class="outline-3">
<h3 id="sec-3-1"><span class="section-number-3">3.1</span> Size <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-3-1">
<ul>
<li>Some formats will not be easily parsed into Excel: eg. JSON, XML
</li>
<li>Word will be slow, or unworkable for GB size data
</li>
<li>CLI provides many composable tools for text manipulation
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-4" class="outline-2">
<h2 id="sec-4"><span class="section-number-2">4</span> Yelp Academic Dataset <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-4">
<ul>
<li><a href="http://yelp.com/academic_dataset">Yelp Data Set</a> covers reviews, users,
businesses
</li>
<li>To download, you'll need to sign up: process takes ~24 hours for approval
</li>
<li>Use .edu email
</li>
</ul>
</div>
<div id="outline-container-4-1" class="outline-3">
<h3 id="sec-4-1"><span class="section-number-3">4.1</span> Example <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-4-1">
<ul>
<li>We'll use this as an example, you can use any data set of your choice
</li>
<li>Just for HW, don't need to use for project
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-5" class="outline-2">
<h2 id="sec-5"><span class="section-number-2">5</span> CLI introduction <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-5">
<ul>
<li>Standard commands available in <a href="http://cli.learncodethehardway.com">Learn CLI the hard way</a>
</li>
<li>All example will be run on <code>ischool.berkeley.edu</code>
</li>
<li>Sheyas and I available for more help
</li>
</ul>
</div>
<div id="outline-container-5-1" class="outline-3">
<h3 id="sec-5-1"><span class="section-number-3">5.1</span> Help <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-5-1">
<ul>
<li>If you're new, don't be intimidated.
</li>
<li>Security policies ensure you can't break anything besides your own files
</li>
<li>Keep backups of important stuff anyway
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-6" class="outline-2">
<h2 id="sec-6"><span class="section-number-2">6</span> <code>wget</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-6">
<ul>
<li>Used for downloading files
</li>
<li>Downloading with the browser is fine, but sometimes nice to use faster
connection, or download it directly to machine you're working on
</li>
</ul>
<pre class="src src-bash">$ wget 'http://www.grouplens.org/system/files/ml-100k.zip'
</pre>
</div>
<div id="outline-container-6-1" class="outline-3">
<h3 id="sec-6-1"><span class="section-number-3">6.1</span> Command <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-6-1">
<ul>
<li>Just <code>wget URL</code>
</li>
<li>I like to use quotes in case there are special characters in the URL, eg
<code>?</code>
</li>
<li>Will download to current directory, same name as remote file
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-7" class="outline-2">
<h2 id="sec-7"><span class="section-number-2">7</span> <code>scp</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-7">
<ul>
<li>Copy a file to or from a remote machine
</li>
<li>Uses same connection as SSH, but copies data instead
</li>
<li>Example: Copy data you've downloaded in your browser
</li>
</ul>
<pre class="src src-bash">$ scp ~/Downloads/ml-100k.zip jblomo@ischool.berkeley.edu:
# or
$ scp ~/Downloads/ml-100k.zip jblomo@ischool.berkeley.edu:i290/movielens-100k.zip
</pre>
</div>
<div id="outline-container-7-1" class="outline-3">
<h3 id="sec-7-1"><span class="section-number-3">7.1</span> Command <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-7-1">
<ul>
<li>Trailing <code>:</code> is important: signifies remote machine
</li>
<li>If you don't specify path or filename, will copy the file with the same
name into your home directory
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-8" class="outline-2">
<h2 id="sec-8"><span class="section-number-2">8</span> <code>gunzip</code> <code>unzip</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-8">
<ul>
<li>Uncompress data sets for simpler, faster manipulation
</li>
</ul>
<pre class="src src-bash">$ unzip ml-100k.zip
# or
$ gunzip yelp_academic_dataset.json.gz
</pre>
</div>
<div id="outline-container-8-1" class="outline-3">
<h3 id="sec-8-1"><span class="section-number-3">8.1</span> Commands <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-8-1">
<dl>
<dt>unzip</dt><dd>expand potentially many file, leave original alone
</dd>
<dt>gunzip</dt><dd>expand original file, leaving only the uncompressed version
</dd>
</dl>
</div>
</div>
</div>
<div id="outline-container-9" class="outline-2">
<h2 id="sec-9"><span class="section-number-2">9</span> <code>less</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-9">
<ul>
<li>View a file
</li>
<li>History: original command was called <code>more</code> to see a file a page at a time
</li>
<li>"Less is more"
</li>
</ul>
<pre class="src src-bash">less yelp_academic_dataset.json
</pre>
</div>
</div>
<div id="outline-container-10" class="outline-2">
<h2 id="sec-10"><span class="section-number-2">10</span> Searching in <code>less</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-10">
<ul>
<li><code>/</code> (forward slash) lets you input search text
</li>
<li><code>q</code> will quit
</li>
</ul>
<pre class="src src-less">/type<span style="color: #8b2252;">": "</span>user<span style="color: #8b2252;">"</span>
<span style="color: #8b2252;">/type"</span>: <span style="color: #8b2252;">"review"</span>
</pre>
</div>
<div id="outline-container-10-1" class="outline-3">
<h3 id="sec-10-1"><span class="section-number-3">10.1</span> Command <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-10-1">
<ul>
<li>Useful for finding specific instances to investigate
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-11" class="outline-2">
<h2 id="sec-11"><span class="section-number-2">11</span> <code>grep</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-11">
<ul>
<li>Find and print lines matching a "regular expression"
</li>
<li><a href="http://www.regular-expressions.info/quickstart.html">Regular expressions</a> are "find" on steroids, but you can use simple strings
</li>
</ul>
<pre class="src src-bash">$ grep 'type<span style="color: #8b2252;">": "</span>review<span style="color: #8b2252;">"' yelp_academic_dataset.json</span>
</pre>
</div>
</div>
<div id="outline-container-12" class="outline-2">
<h2 id="sec-12"><span class="section-number-2">12</span> <code>wc</code> <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-12">
<ul>
<li>"wordcount" counts characters, words, lines
</li>
<li>Most useful in data sets for lines: <code>-l</code>
</li>
</ul>
<pre class="src src-bash">$ wc -l yelp_academic_dataset.json
474434 yelp_academic_dataset.json
</pre>
</div>
</div>
<div id="outline-container-13" class="outline-2">
<h2 id="sec-13"><span class="section-number-2">13</span> Composable <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-13">
<ul>
<li>Genius of Unix: do one thing well, compose commands to get what you want
</li>
<li><code>|</code> pipe characters "sends" output from one program to the input of another
</li>
<li>How many reviews in the data set?
</li>
</ul>
<pre class="src src-bash">$ grep 'type<span style="color: #8b2252;">": "</span>review<span style="color: #8b2252;">"' yelp_academic_dataset.json | wc -l</span>
<span style="color: #8b2252;">330071</span>
<span style="color: #8b2252;">$ egrep -o 'business_id"</span>: <span style="color: #8b2252;">"\w+"</span>' yelp_academic_dataset.json | sort -u | wc -l
9592
</pre>
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<div id="postamble">
<p class="date">Date: 2013-02-01 13:45:14 PST</p>
<p class="author">Author: Jim Blomo</p>
<p class="creator">Org version 7.8.02 with Emacs version 23</p>
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