# Why a histogram?

Annotation category:
Chapter 3

 Note:

Who wants to make a bar chart that's 164 bars long? Or perhaps more to the point, who wants to _read_ your bar chart that's 164 bars long?

You can give it a shot if you want to, but there is a more practical way to display your message. By grouping the data into bins, you can condense the information. Let's look at all the measurements I have between 80 and 90 degrees Fahrenheit:

80.25
83.40
86.46
84.56
82.80
81.15
85.20
89.01
89.23
85.42
87.76

Instead of giving each of these numbers its own special bar, let's group them together in a single range: 80 - 90.

Now, you may note that we lose some information by doing this. Sadly, the viewer of your histogram will never know that the temperature reached a high of 82.80 on June 26th. But we're not focussing on details here; rather we want to draw the viewer's attention to the general trend. Were we to include every data point for every day on our display, not only would it be painstaking work, but it would actually divert attention from the main point and thus undermine the goal of the graph's design.

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