Layers are the key building block of AlgebraOfGraphics. Each layer is the product of the following elementary objects.
- Data (encoding the dataset).
- Mapping (associating variables to plot attributes).
- Visual (encoding data-independent plot information).
- Analyses (encoding transformations that are applied to the data before plotting).
Data, mappings, visuals and analyses can be combined together using Algebraic Operations to form one or more layers.
The output of these algebraic operations can be visualized, as shown in the section Drawing Layers.