R (14) : theme in ggplot2

Set theme elements

Usage

theme(..., complete = FALSE)

Arguments

...

a list of element name, element pairings that modify the existing theme.

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.

Description

Use this function to modify theme settings.

Details

Theme elements can inherit properties from other theme elements. For example, axis.title.x 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.
For more examples of modifying properties using inheritance, see +.gg and %+replace%.
To see a graphical representation of the inheritance tree, see the last example below.

Theme elements

The individual theme elements are:

line	all line elements (element_line)
rect	all rectangluar elements (element_rect)
text	all text elements (element_text)
title	all title elements: plot, axes, legends (element_text; inherits from text)
axis.title	label of axes (element_text; inherits from text)
axis.title.x	x axis label (element_text; inherits from axis.title)
axis.title.y	y axis label (element_text; inherits from axis.title)
axis.text	tick labels along axes (element_text; inherits from text)
axis.text.x	x axis tick labels (element_text; inherits from axis.text)
axis.text.y	y axis tick labels (element_text; inherits from axis.text)
axis.ticks	tick marks along axes (element_line; inherits from line)
axis.ticks.x	x axis tick marks (element_line; inherits from axis.ticks)
axis.ticks.y	y axis tick marks (element_line; inherits from axis.ticks)
axis.ticks.length	length of tick marks (unit)
axis.ticks.margin	space between tick mark and tick label (unit)
axis.line	lines along axes (element_line; inherits from line)
axis.line.x	line along x axis (element_line; inherits from axis.line)
axis.line.y	line along y axis (element_line; inherits from axis.line)
legend.background	background of legend (element_rect; inherits from rect)
legend.margin	extra space added around legend (unit)
legend.key	background underneath legend keys (element_rect; inherits from rect)
legend.key.size	size of legend keys (unit; inherits from legend.key.size)
legend.key.height	key background height (unit; inherits from legend.key.size)
legend.key.width	key background width (unit; inherits from legend.key.size)
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. ("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)
legend.box	arrangement of multiple legends ("horizontal" or "vertical")
panel.background	background of plotting area (element_rect; inherits from rect)
panel.border	border around plotting area (element_rect; inherits from rect)
panel.margin	margin around facet panels (unit)
panel.grid	grid lines (element_line; inherits from line)
panel.grid.major	major grid lines (element_line; inherits from panel.grid)
panel.grid.minor	minor grid lines (element_line; inherits from panel.grid)
panel.grid.major.x	vertical major grid lines (element_line; inherits from panel.grid.major)
panel.grid.major.y	horizontal major grid lines (element_line; inherits from panel.grid.major)
panel.grid.minor.x	vertical minor grid lines (element_line; inherits from panel.grid.minor)
panel.grid.minor.y	horizontal minor grid lines (element_line; inherits from panel.grid.minor)
plot.background	background of the entire plot (element_rect; inherits from rect)
plot.title	plot title (text appearance) (element_text; inherits from title)
plot.margin	margin around entire plot (unit)
strip.background	background of facet labels (element_rect; inherits from rect)
strip.text	facet labels (element_text; inherits from text)
strip.text.x	facet labels along horizontal direction (element_text; inherits from strip.text)
strip.text.y	facet labels along vertical direction (element_text; inherits from strip.text)

Examples

p <- qplot(mpg, wt, data = mtcars)
p




p + theme(panel.background = element_rect(colour = "pink"))




p + theme_bw()




# Scatter plot of gas mileage by vehicle weight
p <- ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point()
# Calculate slope and intercept of line of best fit
coef(lm(mpg ~ wt, data = mtcars))

(Intercept)          wt 
  37.285126   -5.344472 


p + geom_abline(intercept = 37, slope = -5)




# Calculate correlation coefficient
with(mtcars, cor(wt, mpg, use = "everything", method = "pearson"))

[1] -0.8676594


#annotate the plot
p + geom_abline(intercept = 37, slope = -5) +
geom_text(data = data.frame(), aes(4.5, 30, label = "Pearson-R = -.87"))




# Change the axis labels
# Original plot
p




p + xlab("Vehicle Weight") + ylab("Miles per Gallon")




# Or
p + labs(x = "Vehicle Weight", y = "Miles per Gallon")




# Change title appearance
p <- p + labs(title = "Vehicle Weight-Gas Mileage Relationship")
# Set title to twice the base font size
p + theme(plot.title = element_text(size = rel(2)))




p + theme(plot.title = element_text(size = rel(2), colour = "blue"))




# Changing plot look with themes
DF <- data.frame(x = rnorm(400))
m <- ggplot(DF, aes(x = x)) + geom_histogram()
# Default is theme_grey()
m
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




# Compare with
m + theme_bw()
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




# Manipulate Axis Attributes
library(grid) # for unit
m + theme(axis.line = element_line(size = 3, colour = "red", linetype = "dotted"))
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




m + theme(axis.text = element_text(colour = "blue"))
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




m + theme(axis.text.y = element_blank())
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




m + theme(axis.ticks = element_line(size = 2))
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




m + theme(axis.title.y = element_text(size = rel(1.5), angle = 90))
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




m + theme(axis.title.x = element_blank())
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




m + theme(axis.ticks.length = unit(.85, "cm"))
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.




# Legend Attributes
z <- ggplot(mtcars, aes(wt, mpg, colour = factor(cyl))) + geom_point()
z




z + theme(legend.position = "none")




z + theme(legend.position = "bottom")




# Or use relative coordinates between 0 and 1
z + theme(legend.position = c(.5, .5))




z + theme(legend.background = element_rect(colour = "black"))




# Legend margin controls extra space around outside of legend:
z + theme(legend.background = element_rect(), legend.margin = unit(1, "cm"))




z + theme(legend.background = element_rect(), legend.margin = unit(0, "cm"))




# Or to just the keys
z + theme(legend.key = element_rect(colour = "black"))




z + theme(legend.key = element_rect(fill = "yellow"))




z + theme(legend.key.size = unit(2.5, "cm"))




z + theme(legend.text = element_text(size = 20, colour = "red", angle = 45))




z + theme(legend.title = element_text(face = "italic"))




# To change the title of the legend use the name argument
# in one of the scale options
z + scale_colour_brewer(name = "My Legend")




z + scale_colour_grey(name = "Number of \nCylinders")




# Panel and Plot Attributes
z + theme(panel.background = element_rect(fill = "black"))




z + theme(panel.border = element_rect(linetype = "dashed", colour = "black"))




z + theme(panel.grid.major = element_line(colour = "blue"))




z + theme(panel.grid.minor = element_line(colour = "red", linetype = "dotted"))




z + theme(panel.grid.major = element_line(size = 2))




z + theme(panel.grid.major.y = element_blank(), panel.grid.minor.y = element_blank())




z + theme(plot.background = element_rect())




z + theme(plot.background = element_rect(fill = "green"))




# Faceting Attributes
set.seed(4940)
dsmall <- diamonds[sample(nrow(diamonds), 1000), ]
k <- ggplot(dsmall, aes(carat, ..density..)) + geom_histogram(binwidth = 0.2) +
facet_grid(. ~ cut)
k + theme(strip.background = element_rect(colour = "purple", fill = "pink",
                                          size = 3, linetype = "dashed"))




k + theme(strip.text.x = element_text(colour = "red", angle = 45, size = 10,
                                      hjust = 0.5, vjust = 0.5))




k + theme(panel.margin = unit(5, "lines"))




k + theme(panel.margin = unit(0, "lines"))




# Modify a theme and save it
mytheme <- theme_grey() + theme(plot.title = element_text(colour = "red"))
p + mytheme




## Run this to generate a graph of the element inheritance tree
build_element_graph <- function(tree) {
  require(igraph)
  require(plyr)

  inheritdf <- function(name, item) {
    if (length(item$inherit) == 0)
      data.frame()
    else
      data.frame(child = name, parent = item$inherit)
  }

  edges <- rbind.fill(mapply(inheritdf, names(tree), tree))

  # Explicitly add vertices (since not all are in edge list)
  vertices <- data.frame(name = names(tree))
  graph.data.frame(edges, vertices = vertices)
}

g <- build_element_graph(ggplot2:::.element_tree)
Loading required package: igraph

V(g)$label <- V(g)$name

set.seed(324)
par(mar=c(0,0,0,0)) # Remove unnecessary margins




plot(g, layout=layout.fruchterman.reingold, vertex.size=4, vertex.label.dist=.25)

See also

+.gg %+replace% rel

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