What is a stacked chart primarily used for?

A stacked chart is primarily used to extend a bar chart by adding sub-bars for a second categorical variable. This type of chart allows for a visual representation of how different sub-categories contribute to the total of the main category. For example, if you were displaying sales data for different products across various regions, a stacked chart would show the total sales for each region while differentiating each product's contribution with distinct colors or patterns in the bars.

In this way, a stacked chart effectively highlights both the overall totals and the individual components that make up those totals, making it easier to analyze the relationships between categories. This feature is particularly useful when you want to emphasize the breakdown of data within a single category and how those individual parts relate to the whole.

Other types of charts, such as line charts or scatter plots, focus on different aspects of data representation, such as trends over time or relationships between two continuous variables, and do not serve the same purpose as a stacked chart in terms of visualizing the contribution of sub-categories.