Chapter 1

Understanding Data

When you ask people what data is, most reply with a vague description of something that resembles a spreadsheet or a bucket of numbers. The more technically savvy might mention databases or warehouses. However, this is just the format that the data comes in and how it is stored, and it doesn’t say anything about what data is or what any particular dataset represents. It’s an easy trap to fall in because when you ask for data, you usually get a computer file, and it’s hard to think of computer output as anything but just that. Look beyond the file though, and you get something more meaningful.

What Data Represents

Data is more than numbers, and to visualize it, you must know what it represents. Data represents real life. It’s a snapshot of the world in the same way that a photograph captures a small moment in time.

Figure 1-1: A single photo, a single data point


Look at Figure 1-1. If you were to come across this photo, isolated from everything else, and I told you nothing about it, you wouldn’t get much out of it. It’s just another wedding photo. For me though, it’s a happy moment during one of the best days of my life. That’s my wife on the left, all dolled up, and me on the right, wearing something other than jeans and a T-shirt for a change. The pastor who is marrying us is my wife’s uncle, who added a personal touch to the ceremony, and the guy ...

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