“Information is the oil of the 21st century, and analytics is the combustion engine.”
-Peter Sondergaard, Gartner Research
By 2018, it is estimated that companies will spend $114 billion on big data-related projects, an increase of roughly 300%, compared to 2013 (https://www.capgemini-consulting.com/resource-file-access/resource/pdf/big_dat a_pov_03-02-15.pdf). Much of this increase in expenditure is due to how much data is being created and how we are better able to store such data by leveraging distributed filesystems such as Hadoop.
However, collecting the data is only half the battle; the other half involves data extraction, transformation, and loading into a computation system, which leverages the power of modern computers to apply various mathematical methods in order to learn more about data and patterns and extract useful information to make relevant decisions. The entire data workflow has been boosted in the last few years by not only increasing the computation power and providing easily accessible and scalable cloud services (for example, Amazon AWS, Microsoft Azure, and Heroku) but also by a number of tools and libraries that help to easily manage, control, and scale infrastructure and build applications. Such a growth in the computation power also helps to process larger amounts of data and to apply algorithms that were impossible to apply earlier. Finally, various computation- expensive statistical or machine learning algorithms have started to help extract nuggets of information from data.
Finding a uniform definition of data science is akin to tasting wine and comparing flavor profiles among friends—everyone has their own definition and no one description is more accurate than the other. At its core, however, data science is the art of asking intelligent questions about data and receiving intelligent answers that matter to key stakeholders. Unfortunately, the opposite also holds true—ask lousy questions of the data and get lousy answers! Therefore, careful formulation of the question is the key for extracting valuable insights from your data. For this reason, companies are now hiring data scientists to help formulate and ask these questions.
At first, it’s easy to paint a stereotypical picture of what a typical data scientist looks like: t- shirt, sweatpants, thick-rimmed glasses, and debugging a chunk of code in IntelliJ… you get the idea. Aesthetics aside, what are some of the traits of a data scientist? One of our favorite posters describing this role is shown here in the following diagram:
Math, statistics, and general knowledge of computer science is given, but one pitfall that we see among practitioners has to do with understanding the business problem, which goes back to asking intelligent questions of the data. It cannot be emphasized enough: asking more intelligent questions of the data is a function of the data scientist’s understanding of the business problem and the limitations of the data; without this fundamental understanding, even the most intelligent algorithm would be unable to come to solid conclusions based on a wobbly foundation.
A day in the life of a data scientist
This will probably come as a shock to some of you—being a data scientist is more than reading academic papers, researching new tools, and model building until the wee hours of the morning, fueled on espresso; in fact, this is only a small percentage of the time that a data scientist gets to truly play (the espresso part however is 100% true for everyone)! Most part of the day, however, is spent in meetings, gaining a better understanding of the business problem(s), crunching the data to learn its limitations (take heart, this book will expose you to a ton of different feature engineering or feature extractions tasks), and how best to present the findings to non data-sciencey people. This is where the true sausage making process takes place, and the best data scientists are the ones who relish in this process because they are gaining more understanding of the requirements and benchmarks for success. In fact, we could literally write a whole new book describing this process from top-to-tail!
So, what (and who) is involved in asking questions about data? Sometimes, it is process of saving data into a relational database and running SQL queries to find insights into data: “for the millions of users that bought this particular product, what are the top 3 OTHER products also bought?” Other times, the question is more complex, such as, “Given the review of a movie, is this a positive or negative review?” This book is mainly focused on complex questions, like the latter. Answering these types of questions is where businesses really get the most impact from their big data projects and is also where we see a proliferation of emerging technologies that look to make this Q and A system easier, with more functionality.
Some of the most popular, open source frameworks that look to help answer data questions include R, Python, Julia, and Octave, all of which perform reasonably well with small (X < 100 GB) datasets. At this point, it’s worth stopping and pointing out a clear distinction between big versus small data. Our general rule of thumb in the office goes as follows:
If you can open your dataset using Excel, you are working with small data.
Working with big data
What happens when the dataset in question is so vast that it cannot fit into the memory of a single computer and must be distributed across a number of nodes in a large computing cluster? Can’t we just rewrite some R code, for example, and extend it to account for more than a single-node computation? If only things were that simple! There are many reasons why the scaling of algorithms to more machines is difficult. Imagine a simple example of a file containing a list of names:
B
D
X
A
D
A
We would like to compute the number of occurrences of individual words in the file. If the file fits into a single machine, you can easily compute the number of occurrences by using a combination of the Unix tools, sort and uniq:
bash> sort file | uniq -c
The output is as shown ahead:
2 A
1 B
1 D
1 X
However, if the file is huge and distributed over multiple machines, it is necessary to adopt a slightly different computation strategy. For example, compute the number of occurrences of individual words for every part of the file that fits into the memory and merge the results together. Hence, even simple tasks, such as counting the occurrences of names, in a distributed environment can become more complicated.
The above is an excerpt from the book Mastering Machine Learning with Spark 2.x by Alex Tellez, Max Pumperla and Michal Malohlava. If you would like to learn how to solve the above problem and other cool machine learning tasks a data scientist carries out such as the following, check out the book.
- Use Spark streams to cluster tweets online
- Run the PageRank algorithm to compute user influence
- Perform complex manipulation of DataFrames using Spark
- Define Spark pipelines to compose individual data transformations
- Utilize generated models for off-line/on-line prediction
