guide_legend {ggplot2}

Legend guide

Description

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

Usage

guide_legend(
  title = waiver(),
  theme = NULL,
  position = NULL,
  direction = NULL,
  override.aes = list(),
  nrow = NULL,
  ncol = NULL,
  reverse = FALSE,
  order = 0,
  ...
)

Arguments

title

A character string or expression indicating a title of guide. If NULL, the title is not shown. By default (waiver()), the name of the scale object or the name specified in labs() is used for the title.

theme

A theme object to style the guide individually or differently from the plot's theme settings. The theme argument in the guide overrides, and is combined with, the plot's theme.

position

A character string indicating where the legend should be placed relative to the plot panels.

direction

A character string indicating the direction of the guide. One of "horizontal" or "vertical."

override.aes

A list specifying aesthetic parameters of legend key. See details and examples.

nrow, ncol

The desired number of rows and column of legends respectively.

reverse

logical. If TRUE the order of legends is reversed.

order

positive integer less than 99 that specifies the order of this guide among multiple guides. This controls the order in which multiple guides are displayed, not the contents of the guide itself. If 0 (default), the order is determined by a secret algorithm.

...

ignored.

Details

Guides can be specified in each ⁠scale_*⁠ or in guides(). guide = "legend" in ⁠scale_*⁠ is syntactic sugar for guide = guide_legend() (e.g. scale_color_manual(guide = "legend")). As for how to specify the guide for each scale in more detail, see guides().

See Also

The legends section of the online ggplot2 book.

Other guides: guide_bins(), guide_colourbar(), guide_coloursteps(), guides()

Examples

df <- expand.grid(X1 = 1:10, X2 = 1:10)
df$value <- df$X1 * df$X2

p1 <- ggplot(df, aes(X1, X2)) + geom_tile(aes(fill = value))
p2 <- p1 + geom_point(aes(size = value))

# Basic form
p1 + scale_fill_continuous(guide = guide_legend())

# Control styles

# title position
p1 + guides(fill = guide_legend(
  title = "LEFT", theme(legend.title.position = "left")
))

# title text styles via element_text
p1 + guides(fill = guide_legend(theme = theme(
  legend.title = element_text(size = 15, face = "italic", colour = "red")
)))

# label position
p1 + guides(fill = guide_legend(theme = theme(
  legend.text.position = "left",
  legend.text = element_text(hjust = 1)
)))

# label styles
p1 +
  scale_fill_continuous(
    breaks = c(5, 10, 15),
    labels = paste("long", c(5, 10, 15)),
    guide = guide_legend(theme = theme(
      legend.direction = "horizontal",
      legend.title.position = "top",
      legend.text.position = "bottom",
      legend.text = element_text(hjust = 0.5, vjust = 1, angle = 90)
    ))
  )

# Set aesthetic of legend key
# very low alpha value make it difficult to see legend key
p3 <- ggplot(mtcars, aes(vs, am, colour = factor(cyl))) +
  geom_jitter(alpha = 1/5, width = 0.01, height = 0.01)
p3
# override.aes overwrites the alpha
p3 + guides(colour = guide_legend(override.aes = list(alpha = 1)))

# multiple row/col legends
df <- data.frame(x = 1:20, y = 1:20, color = letters[1:20])
p <- ggplot(df, aes(x, y)) +
  geom_point(aes(colour = color))
p + guides(col = guide_legend(nrow = 8))
p + guides(col = guide_legend(ncol = 8))
p + guides(col = guide_legend(nrow = 8, theme = theme(legend.byrow = TRUE)))

# reversed order legend
p + guides(col = guide_legend(reverse = TRUE))