What type of chart is best for visualizing values as percentages of a whole for a single day?

A donut chart is particularly effective for visualizing values as percentages of a whole for a single day because it presents data in a circular format with a hole in the center, making it easy to see proportions at a glance. Each segment represents a category's contribution to the total, allowing viewers to quickly grasp the relative sizes of those segments in comparison to one another. This visualization method is intuitive, especially when aiming to convey the idea of parts making up a whole, such as daily metrics.

In contrast, a stacked area chart is more suited for showing changes over time rather than just displaying parts of a whole at a specific point. A line chart excels in demonstrating trends over time instead of comparing parts to a whole. A number chart generally presents raw figures without relational context, making it less effective for illustrating percentages. Therefore, the characteristics of a donut chart align closely with the need to visualize data as part of a total for a specific day.