Guides for each scale can be set scale-by-scale with the guide argument, or en masse with guides().

Legend type guide shows key (i.e., geoms) mapped onto values. Legend guides for various scales are integrated if possible.

The guides (the axes and legends) help readers interpret your plots. Guides are mostly controlled via the scale (e.g. with the limits, breaks, and labels arguments), but sometimes you will need additional control over guide appearance. Use guides() or the guide argument to individual scales along with guide_*() functions.

Axis guides are the visual representation of position scales like those created with scale_(x|y)_continuous() and scale_(x|y)_discrete().

ggplot2 is an R package for producing visualizations of data. Unlike many graphics packages, ggplot2 uses a conceptual framework based on the grammar of graphics. This allows you to ‘speak’ a graph from composable elements, instead of being limited to a predefined set of charts.

ggplot2 is a system for declaratively creating graphics, based on The Grammar of Graphics. You provide the data, tell ggplot2 how to map variables to aesthetics, what graphical primitives to use, and it takes care of the details.

This is a special guide that can be used to display any graphical object (grob) along with the regular guides. This guide has no associated scale.

ggplot2-specs.Rmd This vignette summarises the various formats that grid drawing functions take. Most of this information is available scattered throughout the R documentation.

Colour bar guide shows continuous colour scales mapped onto values. Colour bar is available with scale_fill and scale_colour. For more information, see the inspiration for this function: Matlab's colorbar function.

The modifying theme components and theme elements sections of the online ggplot2 book.