1. Vinod Gupta School of Management, IIT Kharagpur
Google Refine
Tutorial
April, 08 2012
Sathishwaran.R - 10BM60079
Vijaya Prabhu - 10BM60097
This Tutorial was created using Google Refine Version 2.5 on a Windows 7 platform
2. Data Cleansing
• Data cleansing is identifying the wrong or inaccurate
records in the data set and making appropriate
corrections to the records.
• It involves identifying incomplete, inaccurate, and
incorrect parts of data and then either replacing them
with correct data or deleting the incorrect data
• Data cleansing results in data which is consistent with
the other standard data and is useful for performing
various analysis
• The error in the data could be due to data entry error
by the user, failure during transmission of data or
improper data definitions.
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3. Need for Data Cleansing
• Incorrect or inaccurate data may lead to false
conclusions and can cause investments to be
misdirected in finance.
• Also government needs accurate data on
population and census for directing the funds to
the deserving areas.
• Many organizations tap into customer
information. If the data is not accurate, for eg. If
the address is not accurate then the business
runs the risk of send wrong information, thus
losing customers.
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4. Challenges Data Cleansing
• Loss of Information: In many cases the record may be
incomplete, hence the whole record may require to be
deleted which leads to loss of information. It could
become costly if huge number of data is deleted.
• Maintenance of Data: Once the data is cleansed then
any change in the data specification needs to affect
only the new values. Hence data management
solutions should be designed in such a way that the
process of data entry and retrieval are altered to
provide correct data.
• Data cleansing is an iterative process which needs
significant work in exploration and corrction of entries.
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5. About Google Refine
• Google Refine is a powerful tool that can be effectively
used for data cleansing.
• It helps in working with raw data, cleaning it up,
transforming from one format to other, encompassing
it with web services and linking it to databases.
• It is very easy to use and has a web interface.
• It is freely available and works well with any browser.
• Google Refine is a desktop application and it runs a
small web server on your system and we need to point
our browser to the server to use refine.
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6. Getting Started - Installation
1. Download the zip file (appropriate Windows,
Mac, Linux versions) from the link
http://code.google.com/p/google-
refine/wiki/Downloads?tm=2
2. Uncompress the files from the zip file.
3. Run the “google-refine.exe” file.
4. A command window opens and Google refine
runs taking the user to the home page in the
default browser.
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8. Importing Data
• Google Refine supports TSV, CSV, Excel (.xls
and .xlsx), JSON, XML, and Google data
document formats.
• Once imported the data is in Google Refine’s
own data format.
• We have used TSV data on Disasters
worldwide from 1900-2008 available from
http://www.infochimps.com/datasets/disaster
s-worldwide-from-1900-2008 for the tutorial.
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13. Faceting
• Faceting is about seeing the big picture and
filtering based on rows to work on data you
want to change in bulk.
• We can create a facet for a column to get the
details about that column and then we can
filter to a subset of rows with a constraint.
• We can perform text facet, Numeric facet,
timeline facet and scatterplot facet. Also
various customized facets can be designed.
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34. Data Augmentation
• Reconciliation option in Google refine allows
data to be linked to web pages. Suppose we
want details on the country where the
calamity has struck we can perform the
following steps
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