theme_get: Get, set, and modify the active theme

Description

The current/active theme is automatically applied to every plot you draw. Use theme_get to get the current theme, and theme_set to completely override it. theme_update and theme_replace are shorthands for changing individual elements.

Usage

theme_get()
theme_set(new)
theme_update(...)
theme_replace(...)
e1 %+replace% e2

Arguments

new

new theme (a list of theme elements)

...

named list of theme settings

e1, e2

Theme and element to combine

Value

theme_set, theme_update, and theme_replace invisibly return the previous theme so you can easily save it, then later restore it.

Adding on to a theme

+ and %+replace% can be used to modify elements in themes. + updates the elements of e1 that differ from elements specified (not NULL) in e2. Thus this operator can be used to incrementally add or modify attributes of a ggplot theme. In contrast, %+replace% replaces the entire element; any element of a theme not specified in e2 will not be present in the resulting theme (i.e. NULL). Thus this operator can be used to overwrite an entire theme. theme_update uses the + operator, so that any unspecified values in the theme element will default to the values they are set in the theme. theme_replace uses %+replace% tocompletely replace the element, so any unspecified values will overwrite the current value in the theme with NULLs.

Examples

Run this code

p <- ggplot(mtcars, aes(mpg, wt)) +
  geom_point()
p

# Use theme_set() to completely override the current theme.
# Here we have the old theme so we can later restore it.
# Note that the theme is applied when the plot is drawn, not
# when it is created.
old <- theme_set(theme_bw())
p
theme_set(old)
p


# Modifying theme objects -----------------------------------------
# You can use + and %+replace% to modify a theme object.
# They differ in how they deal with missing arguments in
# the theme elements.

add_el <- theme_grey() +
  theme(text = element_text(family = "Times"))
add_el$text

rep_el <- theme_grey() %+replace%
  theme(text = element_text(family = "Times"))
rep_el$text

# theme_update() and theme_replace() are similar except they
# apply directly to the current/active theme.