Data science

Dejan Sarka

Interview questions and answers about data science, data understanding and preparation

July 27, 2018 by

Q1: In the data science terminology, how do you call the data that you analyze?

In data science, you analyze datasets. Datasets consists of cases, which are the entities you analyze. Cases are described by their variables, which represent the attributes of the entities. The first important question you need to answer when you start a data science project is what exactly is your case. Is this a person, a family, an order? Then you collect all of the knowledge about each case you can get and store this information in the variables.

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Dejan Sarka

Data science, data understanding and preparation – grouping and aggregating data

July 10, 2018 by

I already tacitly did quite a few aggregations over the whole dataset and aggregations over groups of data. Of course, the vast majority of the readers here is familiar with the GROUP BY clause in the T-SQL SELECT statement and with the basic aggregate functions. Therefore, in this article, I want to show some advanced aggregation options in T-SQL and grouping in aggregations of data in an R or a Python data frame.

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Dejan Sarka

Data science, data understanding and preparation – basic work with datasets

June 4, 2018 by

In my previous four articles, I worked on a single variable of a dataset. I have shown example code in T-SQL, R, and Python languages. I always used the same dataset. Therefore, you might have gotten the impression that in R and in Python, you can operate on a dataset the same way like you operate on an SQL Server table. However, there is a big difference between an SQL Server table and Python or R data frame.

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Dejan Sarka

Data science, data understanding and preparation – entropy of a discrete variable

May 14, 2018 by

In the conclusion of my last article, Data science, data understanding and preparation – binning a continuous variable, I wrote something about preserving the information when you bin a continuous variable to bins with an equal number of cases. I am explaining this sentence in this article you are currently reading. I will show you how to calculate the information stored in a discrete variable by explaining the measure for the information, namely the entropy.

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Dejan Sarka

Data science, data understanding and preparation – binning a continuous variable

April 23, 2018 by

I started to explain the data preparation part of a data science project with discrete variables. As you should know by now, discrete variables can be categorical or ordinal. For ordinal, you have to define the order either through the values of the variable or inform about the order the R or the Python execution engine. Let me start this article with Python code that shows another way how to define the order of the Education variable from the dbo.vTargetMail view from the AdventureWorksDW2016 demo database.

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Dejan Sarka

Data science, data understanding and preparation – ordinal variables and dummies

March 29, 2018 by

In my previous article, Introduction to data science, data understanding and preparation, I showed how to make an overview of a distribution of a discrete variable. I analyzed the NumberCarsOwned variable from the dbo.vTargetMail view that you can find in the AdventureWorksDW2016 demo database. The graphs I created in R and Python and the histogram created with T-SQL were all very nice. Now let me try to create a histogram for another variable from that view, for the Education variable. I am starting with R, as you can see from the following code.

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Dejan Sarka

Introduction to data science, data understanding and preparation

March 14, 2018 by

Data science, machine learning, data mining, advanced analytics, or however you want to name it, is a hot topic these days. Many people would like to start some project in this area. However, very soon after the start you realize you have a huge problem: your data. Your data might come from your line of business applications, data warehouses, or even external sources. Typically, it is not prepared for applying advanced analytical algorithms on it straight out of the source. In addition, you have to understand your data thoroughly, otherwise you might feed the algorithms with inappropriate variables. Soon you learn the fact that is well known to seasoned data scientists: you spend around 70-80% of the time dedicated to a data science project on data preparation and understanding.

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Minette Steynberg

10 things you need to know to become a Data Scientist

August 22, 2016 by

Introduction

If you have been browsing job ads lately, you would have noticed a huge amount of positions available for Data Scientist. The demand seems to be much larger than the supply which means that there is a huge opportunity here. However, there appears to be a catch: Most of these positions requires some experience or knowledge in the field of Data Science. So if you want midway through your career, how can you skill up to become a Data Scientist?

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