The bar chart is the most commonly-used data visualization chart. It has many applications, and we will see it often in this course. Right now, we'll learn how the bar chart shows the distribution of categorical variables.
The bar chart (also called a bar graph) presents the values for one categorical variable. It has two axes. The categorical axis (shown as the horizontal axis) tells us the groups defined by this variable. The numerical axis (shown as the vertical axis) shows the values for each group. In this case, these values are frequencies.
The length of the bars is the most important part of a bar graph; this is what represents the actual values of each variable. The longer or taller the bar, the larger the value represented. The width of the bars and the space between them doesn't mean anything; we can design them as we like.