Modify components of a theme

Source: R/theme.r

Themes are a powerful way to customize the non-data components of your plots: i.e. titles, labels, fonts, background, gridlines, and legends. Themes can be used to give plots a consistent customized look. Modify a single plot's theme using theme(); see theme_update() if you want modify the active theme, to affect all subsequent plots. Theme elements are documented together according to inheritance, read more about theme inheritance below.

theme(line, rect, text, title, aspect.ratio, axis.title, axis.title.x,
  axis.title.x.top, axis.title.x.bottom, axis.title.y, axis.title.y.left,
  axis.title.y.right, axis.text, axis.text.x, axis.text.x.top,
  axis.text.x.bottom, axis.text.y, axis.text.y.left, axis.text.y.right,
  axis.ticks, axis.ticks.x, axis.ticks.x.top, axis.ticks.x.bottom,
  axis.ticks.y, axis.ticks.y.left, axis.ticks.y.right, axis.ticks.length,
  axis.ticks.length.x, axis.ticks.length.x.top, axis.ticks.length.x.bottom,
  axis.ticks.length.y, axis.ticks.length.y.left, axis.ticks.length.y.right,
  axis.line, axis.line.x, axis.line.x.top, axis.line.x.bottom, axis.line.y,
  axis.line.y.left, axis.line.y.right, legend.background, legend.margin,
  legend.spacing, legend.spacing.x, legend.spacing.y, legend.key,
  legend.key.size, legend.key.height, legend.key.width, legend.text,
  legend.text.align, legend.title, legend.title.align, legend.position,
  legend.direction, legend.justification, legend.box, legend.box.just,
  legend.box.margin, legend.box.background, legend.box.spacing,
  panel.background, panel.border, panel.spacing, panel.spacing.x,
  panel.spacing.y, panel.grid, panel.grid.major, panel.grid.minor,
  panel.grid.major.x, panel.grid.major.y, panel.grid.minor.x,
  panel.grid.minor.y, panel.ontop, plot.background, plot.title,
  plot.subtitle, plot.caption, plot.tag, plot.tag.position, plot.margin,
  strip.background, strip.background.x, strip.background.y,
  strip.placement, strip.text, strip.text.x, strip.text.y,
  strip.switch.pad.grid, strip.switch.pad.wrap, ..., complete = FALSE,
  validate = TRUE)

Arguments

line

all line elements (element_line())
rect

all rectangular elements (element_rect())
text

all text elements (element_text())
title

all title elements: plot, axes, legends (element_text(); inherits from text)
aspect.ratio

aspect ratio of the panel
axis.title, axis.title.x, axis.title.y, axis.title.x.top, axis.title.x.bottom, axis.title.y.left, axis.title.y.right

labels of axes (element_text()). Specify all axes' labels (axis.title), labels by plane (using axis.title.x or axis.title.y), or individually for each axis (using axis.title.x.bottom, axis.title.x.top, axis.title.y.left, axis.title.y.right). axis.title.*.* inherits from axis.title.* which inherits from axis.title, which in turn inherits from text
axis.text, axis.text.x, axis.text.y, axis.text.x.top, axis.text.x.bottom, axis.text.y.left, axis.text.y.right

tick labels along axes (element_text()). Specify all axis tick labels (axis.text), tick labels by plane (using axis.text.x or axis.text.y), or individually for each axis (using axis.text.x.bottom, axis.text.x.top, axis.text.y.left, axis.text.y.right). axis.text.*.* inherits from axis.text.* which inherits from axis.text, which in turn inherits from text
axis.ticks, axis.ticks.x, axis.ticks.x.top, axis.ticks.x.bottom, axis.ticks.y, axis.ticks.y.left, axis.ticks.y.right

tick marks along axes (element_line()). Specify all tick marks (axis.ticks), ticks by plane (using axis.ticks.x or axis.ticks.y), or individually for each axis (using axis.ticks.x.bottom, axis.ticks.x.top, axis.ticks.y.left, axis.ticks.y.right). axis.ticks.*.* inherits from axis.ticks.* which inherits from axis.ticks, which in turn inherits from line
axis.ticks.length, axis.ticks.length.x, axis.ticks.length.x.top, axis.ticks.length.x.bottom, axis.ticks.length.y, axis.ticks.length.y.left, axis.ticks.length.y.right

length of tick marks (unit)
axis.line, axis.line.x, axis.line.x.top, axis.line.x.bottom, axis.line.y, axis.line.y.left, axis.line.y.right

lines along axes (element_line()). Specify lines along all axes (axis.line), lines for each plane (using axis.line.x or axis.line.y), or individually for each axis (using axis.line.x.bottom, axis.line.x.top, axis.line.y.left, axis.line.y.right). axis.line.*.* inherits from axis.line.* which inherits from axis.line, which in turn inherits from line
legend.background

background of legend (element_rect(); inherits from rect)
legend.margin

the margin around each legend (margin())
legend.spacing, legend.spacing.x, legend.spacing.y

the spacing between legends (unit). legend.spacing.x & legend.spacing.y inherit from legend.spacing or can be specified separately
legend.key

background underneath legend keys (element_rect(); inherits from rect)
legend.key.size, legend.key.height, legend.key.width

size of legend keys (unit); key background height & width inherit from legend.key.size or can be specified separately
legend.text

legend item labels (element_text(); inherits from text)
legend.text.align

alignment of legend labels (number from 0 (left) to 1 (right))
legend.title

title of legend (element_text(); inherits from title)
legend.title.align

alignment of legend title (number from 0 (left) to 1 (right))
legend.position

the position of legends ("none", "left", "right", "bottom", "top", or two-element numeric vector)
legend.direction

layout of items in legends ("horizontal" or "vertical")
legend.justification

anchor point for positioning legend inside plot ("center" or two-element numeric vector) or the justification according to the plot area when positioned outside the plot
legend.box

arrangement of multiple legends ("horizontal" or "vertical")
legend.box.just

justification of each legend within the overall bounding box, when there are multiple legends ("top", "bottom", "left", or "right")
legend.box.margin

margins around the full legend area, as specified using margin()
legend.box.background

background of legend area (element_rect(); inherits from rect)
legend.box.spacing

The spacing between the plotting area and the legend box (unit)
panel.background

background of plotting area, drawn underneath plot (element_rect(); inherits from rect)
panel.border

border around plotting area, drawn on top of plot so that it covers tick marks and grid lines. This should be used with fill = NA (element_rect(); inherits from rect)
panel.spacing, panel.spacing.x, panel.spacing.y

spacing between facet panels (unit). panel.spacing.x & panel.spacing.y inherit from panel.spacing or can be specified separately.
panel.grid, panel.grid.major, panel.grid.minor, panel.grid.major.x, panel.grid.major.y, panel.grid.minor.x, panel.grid.minor.y

grid lines (element_line()). Specify major grid lines, or minor grid lines separately (using panel.grid.major or panel.grid.minor) or individually for each axis (using panel.grid.major.x, panel.grid.minor.x, panel.grid.major.y, panel.grid.minor.y). Y axis grid lines are horizontal and x axis grid lines are vertical. panel.grid.*.* inherits from panel.grid.* which inherits from panel.grid, which in turn inherits from line
panel.ontop

option to place the panel (background, gridlines) over the data layers (logical). Usually used with a transparent or blank panel.background.
plot.background

background of the entire plot (element_rect(); inherits from rect)
plot.title

plot title (text appearance) (element_text(); inherits from title) left-aligned by default
plot.subtitle

plot subtitle (text appearance) (element_text(); inherits from title) left-aligned by default
plot.caption

caption below the plot (text appearance) (element_text(); inherits from title) right-aligned by default
plot.tag

upper-left label to identify a plot (text appearance) (element_text(); inherits from title) left-aligned by default
plot.tag.position

The position of the tag as a string ("topleft", "top", "topright", "left", "right", "bottomleft", "bottom", "bottomright) or a coordinate. If a string, extra space will be added to accommodate the tag.
plot.margin

margin around entire plot (unit with the sizes of the top, right, bottom, and left margins)
strip.background, strip.background.x, strip.background.y

background of facet labels (element_rect(); inherits from rect). Horizontal facet background (strip.background.x) & vertical facet background (strip.background.y) inherit from strip.background or can be specified separately
strip.placement

placement of strip with respect to axes, either "inside" or "outside". Only important when axes and strips are on the same side of the plot.
strip.text, strip.text.x, strip.text.y

facet labels (element_text(); inherits from text). Horizontal facet labels (strip.text.x) & vertical facet labels (strip.text.y) inherit from strip.text or can be specified separately
strip.switch.pad.grid

space between strips and axes when strips are switched (unit)
strip.switch.pad.wrap

space between strips and axes when strips are switched (unit)
...

additional element specifications not part of base ggplot2. If supplied validate needs to be set to FALSE.
complete

set this to TRUE if this is a complete theme, such as the one returned by theme_grey(). Complete themes behave differently when added to a ggplot object. Also, when setting complete = TRUE all elements will be set to inherit from blank elements.
validate

TRUE to run validate_element(), FALSE to bypass checks.

Theme inheritance

Theme elements inherit properties from other theme elements heirarchically. For example, axis.title.x.bottom inherits from axis.title.x which inherits from axis.title, which in turn inherits from text. All text elements inherit directly or indirectly from text; all lines inherit from line, and all rectangular objects inherit from rect. This means that you can modify the appearance of multiple elements by setting a single high-level component.

Learn more about setting these aesthetics in vignette("ggplot2-specs").

See also

+.gg() and %+replace%, element_blank(), element_line(), element_rect(), and element_text() for details of the specific theme elements.

Examples

p1 <- ggplot(mtcars, aes(wt, mpg)) +
  geom_point() +
  labs(title = "Fuel economy declines as weight increases")
p1

# Plot ---------------------------------------------------------------------
p1 + theme(plot.title = element_text(size = rel(2)))
p1 + theme(plot.background = element_rect(fill = "green"))

# Panels --------------------------------------------------------------------

p1 + theme(panel.background = element_rect(fill = "white", colour = "grey50"))
p1 + theme(panel.border = element_rect(linetype = "dashed", fill = NA))
p1 + theme(panel.grid.major = element_line(colour = "black"))
p1 + theme(
  panel.grid.major.y = element_blank(),
  panel.grid.minor.y = element_blank()
)

# Put gridlines on top of data
p1 + theme(
  panel.background = element_rect(fill = NA),
  panel.grid.major = element_line(colour = "grey50"),
  panel.ontop = TRUE
)

# Axes ----------------------------------------------------------------------
# Change styles of axes texts and lines
p1 + theme(axis.line = element_line(size = 3, colour = "grey80"))
p1 + theme(axis.text = element_text(colour = "blue"))
p1 + theme(axis.ticks = element_line(size = 2))

# Change the appearance of the y-axis title
p1 + theme(axis.title.y = element_text(size = rel(1.5), angle = 90))

# Make ticks point outwards on y-axis and inwards on x-axis
p1 + theme(
  axis.ticks.length.y = unit(.25, "cm"),
  axis.ticks.length.x = unit(-.25, "cm"),
  axis.text.x = element_text(margin = margin(t = .3, unit = "cm"))
)

# \donttest{
# Legend --------------------------------------------------------------------
p2 <- ggplot(mtcars, aes(wt, mpg)) +
  geom_point(aes(colour = factor(cyl), shape = factor(vs))) +
  labs(
    x = "Weight (1000 lbs)",
    y = "Fuel economy (mpg)",
    colour = "Cylinders",
    shape = "Transmission"
   )
p2

# Position
p2 + theme(legend.position = "none")
p2 + theme(legend.justification = "top")
p2 + theme(legend.position = "bottom")

# Or place legends inside the plot using relative coordinates between 0 and 1
# legend.justification sets the corner that the position refers to
p2 + theme(
  legend.position = c(.95, .95),
  legend.justification = c("right", "top"),
  legend.box.just = "right",
  legend.margin = margin(6, 6, 6, 6)
)

# The legend.box properties work similarly for the space around
# all the legends
p2 + theme(
  legend.box.background = element_rect(),
  legend.box.margin = margin(6, 6, 6, 6)
)

# You can also control the display of the keys
# and the justification related to the plot area can be set
p2 + theme(legend.key = element_rect(fill = "white", colour = "black"))
p2 + theme(legend.text = element_text(size = 8, colour = "red"))
p2 + theme(legend.title = element_text(face = "bold"))

# Strips --------------------------------------------------------------------

p3 <- ggplot(mtcars, aes(wt, mpg)) +
  geom_point() +
  facet_wrap(~ cyl)
p3

p3 + theme(strip.background = element_rect(colour = "black", fill = "white"))
p3 + theme(strip.text.x = element_text(colour = "white", face = "bold"))
p3 + theme(panel.spacing = unit(1, "lines"))
# }