Data is the most important part of the chart, but it's also just the beginning of the process. Next, we must consider what we want to do with the data. Do we want to explore its range, see its minimum and maximum values (e.g. the range of income levels in a country)? Or do we want to understand what factors influence the outcome of something (e.g. how income level affects shopping habits)?

There are many possible questions here. Before starting to visualize anything, you should decide on the story you want to tell with the data. In this course, we will teach you to recognize the four main data visualization goals:

• The distribution - what is the range of the values? what is the minimum value? what is the maximum value? which values are typical? are there any patterns in the data?
• The composition (or parts of the whole) - what parts is the whole set made of? what proportion do each value contribute?
• Change over time - how does the values change with time? do values increase with time? do they decrease with time? are there seasonal trends?
• Relationships - are the variables correlated? does great value of one variable lead to great value of another variable?

You can think of each of these goals as a story. Each chapter in our course will explain one of these four stories. Chapters will also have a "story" section called 'Know your problem'. Although the data's story might appear obvious, sometimes it can surprise you! The difference between goals for the same data can be subtle; recognizing them will take some work. Therefore, we will use the story section to teach you how to recognize your story by asking the right questions. Then, later in the chapter, we will try to answer the questions using the chart we've created.