Combining Multiple Geoms and Layers

Layering is a core concept in ggplot2 that lets you build complex visualizations by combining multiple geometric objects, or geoms, in a single plot. Each geom represents a different way to display your data, such as points, lines, or bars. By stacking geoms, you can reveal different aspects of your dataset within the same visual context. For instance, you might want to show both raw data points and a fitted trend line to help viewers understand patterns and relationships in your data.

The order in which you add geoms and layers in your plot code can affect the final appearance. Layers added later in your ggplot call are drawn on top of earlier ones. For example, if you place geom_point() before geom_smooth(), the points will appear beneath the smooth line. Reversing the order would draw the line first, potentially hiding it behind the points. By carefully choosing the layering order, you control which visual elements stand out and how different data features are emphasized.