Welcome! My name is Andrea Giussani, and I am going to be your instructor for this course on data visualization with Python using Matplotlib.

This course will guide you through all the possible techniques that are used to visualize data using the python language, and that will help you become a data viz ninja.

In particular, we will focus on the most important data visualization library in python, Matplotlib, which is the benchmark in Python when we want to plot data.

In this course, we will explore the main functionalities of Matplotlib, we will look at how to customize the Matplotlib objects, we will also dive into different plotting techniques, and finally, we will focus on how to communicate results.

By the end of this course, you will be able to produce stunning plots that will definitely increase the value of your work. The data we will use is available on the course-specific GitHub repository: so please feel free to go there and download it, and follow along with the course.

As a data scientist, you often have to communicate relevant information to colleagues, information that generally comes either from exploratory data analysis or from a sophisticated machine learning algorithm. This is indeed a very important step, since the way in which we present those insights has a direct impact on the perception of the importance of those results from a business point of view.

So the question is: how do we effectively communicate those results with our colleagues? 

Take, for instance, the following dataset:

This shows the first 5 rows of the Gapminder dataset. The Gapminder dataset contains different variables for each country, such as population size, life expectancy, GDP per capita, babies per woman, and Child Mortality rate (under five years of age) for different years. It goes from 1964 through to recent years. In this example, we are taking into account the year 2012.

Suppose that we are interested in the relationship between GDP and life expectancy, and how it’s evolved over time.

We could take the raw dataset, and say, apply a regression model on the data to infer the quantitative relationship between those features.

This is fine, but in many cases, we want to understand the data at a glance. 

To do so, instead of looking at the raw data table, we could perform Exploratory Data Analysis, EDA in short, and understand the patterns in our data… but in practice, we typically synthesize the aforementioned information into a picture, such as this one.

It looks much better, doesn’t it?

Now the question is: what can we infer from this picture? Well, quite a lot actually!

Firstly, note that the size of the bubble represents the population size.

But the most interesting one is that the relationship is not linear. So, if we had applied a linear regression model to this data, it would have been the wrong one, with the consequence of obtaining an unreliable estimation. 

As a consequence, visualizing the raw dataset before any sophisticated analysis is very important.  Indeed, visualizing data can be very effective especially in the initial phase of a data science project, where we have to choose a model for our data. This will definitely depend on the patterns identified in the data during the visualization phase.

Furthermore, showing an effective plot during a meeting could be more explicative and persuasive than explaining the quantitative analysis performed on the raw data. Indeed, many people in business do not have a quantitative background, and therefore it is important to easily translate that information in a way that is easy to understand for everybody.

All the techniques that transform raw data into a sort of visual representation fall into the discipline of Data Visualization. 

With the term Data Visualization we could be referring to the process of transforming raw data into an embedded graphical dimension, which borders with descriptive statistics, graphical design, and storytelling; but more importantly, data viz techniques are used extensively in different departments of companies to communicate their work to a broader audience.

Data visualization is a complex field, with many different domains of application. Please, note that this course will mainly focus on data analysis.

Ok, we have understood the importance of data visualization. It’s now time to understand how we perform data visualization. To do so, we will use the Python language, and use the Matplotlib library to perform data visualization. Let’s dive into it; see you in the next lecture.

Lectures

Introduction to Matplotlib - Customization in Matplotlib - Multiple Plots in Matplotlib - Annotating Text with Matplotlib - Advanced Customization in Matplotlib - Different Plot Types in Matplotlib - Conclusion