In a chart, which axis should always represent numeric values?

In a chart, the Y axis is typically where numeric values are represented. This convention helps in visually illustrating the relationship between a dependent variable and an independent variable, which are often plotted on the Y and X axes, respectively. In many types of charts, such as line graphs and bar charts, the Y axis indicates magnitude, allowing viewers to easily see how a quantity changes in relation to another metric.

The Y axis is essential for displaying data that shows variation, while the X axis usually represents categories or values that are not inherently numeric, such as time periods or categories of items. This structure facilitates clear data interpretation, where the viewer can quickly analyze trends and compare different data points based on the numeric values shown on the Y axis.

In specialized charts, such as three-dimensional plots, there may be a Z axis to account for an additional dimension; however, in standard two-dimensional charts, the numeric representation is primarily focused on the Y axis.