Book Image

Expert Data Modeling with Power BI

By : Soheil Bakhshi
Book Image

Expert Data Modeling with Power BI

By: Soheil Bakhshi

Overview of this book

This book is a comprehensive guide to understanding the ins and outs of data modeling and how to create data models using Power BI confidently. You'll learn how to connect data from multiple sources, understand data, define and manage relationships between data, and shape data models to gain deep and detailed insights about your organization. In this book, you'll explore how to use data modeling and navigation techniques to define relationships and create a data model before defining new metrics and performing custom calculations using modeling features. As you advance through the chapters, the book will demonstrate how to create full-fledged data models, enabling you to create efficient data models and simpler DAX code with new data modeling features. With the help of examples, you'll discover how you can solve business challenges by building optimal data models and changing your existing data models to meet evolving business requirements. Finally, you'll learn how to use some new and advanced modeling features to enhance your data models to carry out a wide variety of complex tasks. By the end of this Power BI book, you'll have gained the skills you need to structure data coming from multiple sources in different ways to create optimized data models that support reporting and data analytics.
Table of Contents (18 chapters)
Section 1: Data Modeling in Power BI
Section 2: Data Preparation in Query Editor
Section 3: Data Modeling
Section 4: Advanced Data Modeling

Understanding custom functions

In many cases, we may face a situation where we repeatedly need to calculate something. In such cases, it makes absolute sense to create a custom function that takes care of all the calculation logic needed. After defining a custom function, we can invoke this function many times. As stated in the Introduction to Power Query M formula language in Power BI section, under Function value, we can create a custom function by putting the list of parameters (if any) in parentheses, along with the output data type and the goes-to symbol =>, followed by a definition of the function.

The following example shows a straightforward form of a custom function that gets a date input and adds one day to it:

SimpleFunction = (DateValue as date) as date =>
Date.AddDays(DateValue, 1)

We can simply invoke the preceding function as follows:


The result of invoking the function is 2/01/2020.

We can define a custom function...