So far have mostly discussed how to get the data displayed the way you want, focusing on the essence of the plot.

Themes give you a huge amount of control over the appearance of the plot, the choice of background colours, fonts and so on.

p <- qplot(carat, price, data = diamonds, colour = clarity); p

p + theme_bw()

Tufte theme

library(ggthemes)
p + theme_tufte()

Economist theme

p + theme_economist() + scale_colour_economist() 

Excel 2003 theme

p + theme_excel() + scale_colour_excel()

## Warning: This manual palette can handle a maximum of 7 values. You have
## supplied 8.

## Warning: This manual palette can handle a maximum of 7 values. You have
## supplied 8.

Wall street journal theme

p + theme_wsj()

You can set a theme for all plots:

theme_set(theme_bw())

We can also take a look at options for each theme:

theme_bw()

## List of 44
##  $ line                 :List of 4
##   ..$ colour  : chr "black"
##   ..$ size    : num 0.5
##   ..$ linetype: num 1
##   ..$ lineend : chr "butt"
##   ..- attr(*, "class")= chr [1:2] "element_line" "element"
##  $ rect                 :List of 4
##   ..$ fill    : chr "white"
##   ..$ colour  : chr "black"
##   ..$ size    : num 0.5
##   ..$ linetype: num 1
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ text                 :List of 10
##   ..$ family    : chr ""
##   ..$ face      : chr "plain"
##   ..$ colour    : chr "black"
##   ..$ size      : num 12
##   ..$ hjust     : num 0.5
##   ..$ vjust     : num 0.5
##   ..$ angle     : num 0
##   ..$ lineheight: num 0.9
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 0 0 0 0
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : logi FALSE
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ axis.line            :List of 4
##   ..$ colour  : NULL
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..$ lineend : NULL
##   ..- attr(*, "class")= chr [1:2] "element_line" "element"
##  $ axis.line.x          : list()
##   ..- attr(*, "class")= chr [1:2] "element_blank" "element"
##  $ axis.line.y          : list()
##   ..- attr(*, "class")= chr [1:2] "element_blank" "element"
##  $ axis.text            :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      :Class 'rel'  num 0.8
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    : NULL
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ axis.text.x          :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : NULL
##   ..$ vjust     : num 1
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 2.4 0 0 0
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ axis.text.y          :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : num 1
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 0 2.4 0 0
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ axis.ticks           :List of 4
##   ..$ colour  : chr "black"
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..$ lineend : NULL
##   ..- attr(*, "class")= chr [1:2] "element_line" "element"
##  $ axis.ticks.length    :Class 'unit'  atomic [1:1] 3
##   .. ..- attr(*, "valid.unit")= int 8
##   .. ..- attr(*, "unit")= chr "pt"
##  $ axis.title.x         :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 4.8 0 2.4 0
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ axis.title.y         :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : num 90
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 0 4.8 0 2.4
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ legend.background    :List of 4
##   ..$ fill    : NULL
##   ..$ colour  : logi NA
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ legend.margin        :Class 'unit'  atomic [1:1] 0.2
##   .. ..- attr(*, "valid.unit")= int 1
##   .. ..- attr(*, "unit")= chr "cm"
##  $ legend.key           :List of 4
##   ..$ fill    : NULL
##   ..$ colour  : chr "grey80"
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ legend.key.size      :Class 'unit'  atomic [1:1] 1.2
##   .. ..- attr(*, "valid.unit")= int 3
##   .. ..- attr(*, "unit")= chr "lines"
##  $ legend.key.height    : NULL
##  $ legend.key.width     : NULL
##  $ legend.text          :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      :Class 'rel'  num 0.8
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    : NULL
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ legend.text.align    : NULL
##  $ legend.title         :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : num 0
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    : NULL
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ legend.title.align   : NULL
##  $ legend.position      : chr "right"
##  $ legend.direction     : NULL
##  $ legend.justification : chr "center"
##  $ legend.box           : NULL
##  $ panel.background     :List of 4
##   ..$ fill    : chr "white"
##   ..$ colour  : logi NA
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ panel.border         :List of 4
##   ..$ fill    : logi NA
##   ..$ colour  : chr "grey50"
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ panel.grid.major     :List of 4
##   ..$ colour  : chr "grey90"
##   ..$ size    : num 0.2
##   ..$ linetype: NULL
##   ..$ lineend : NULL
##   ..- attr(*, "class")= chr [1:2] "element_line" "element"
##  $ panel.grid.minor     :List of 4
##   ..$ colour  : chr "grey98"
##   ..$ size    : num 0.5
##   ..$ linetype: NULL
##   ..$ lineend : NULL
##   ..- attr(*, "class")= chr [1:2] "element_line" "element"
##  $ panel.margin         :Class 'unit'  atomic [1:1] 6
##   .. ..- attr(*, "valid.unit")= int 8
##   .. ..- attr(*, "unit")= chr "pt"
##  $ panel.margin.x       : NULL
##  $ panel.margin.y       : NULL
##  $ panel.ontop          : logi FALSE
##  $ strip.background     :List of 4
##   ..$ fill    : chr "grey80"
##   ..$ colour  : chr "grey50"
##   ..$ size    : num 0.2
##   ..$ linetype: NULL
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ strip.text           :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : chr "grey10"
##   ..$ size      :Class 'rel'  num 0.8
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    : NULL
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ strip.text.x         :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 6 0 6 0
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ strip.text.y         :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      : NULL
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : num -90
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 0 6 0 6
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ strip.switch.pad.grid:Class 'unit'  atomic [1:1] 0.1
##   .. ..- attr(*, "valid.unit")= int 1
##   .. ..- attr(*, "unit")= chr "cm"
##  $ strip.switch.pad.wrap:Class 'unit'  atomic [1:1] 0.1
##   .. ..- attr(*, "valid.unit")= int 1
##   .. ..- attr(*, "unit")= chr "cm"
##  $ plot.background      :List of 4
##   ..$ fill    : NULL
##   ..$ colour  : chr "white"
##   ..$ size    : NULL
##   ..$ linetype: NULL
##   ..- attr(*, "class")= chr [1:2] "element_rect" "element"
##  $ plot.title           :List of 10
##   ..$ family    : NULL
##   ..$ face      : NULL
##   ..$ colour    : NULL
##   ..$ size      :Class 'rel'  num 1.2
##   ..$ hjust     : NULL
##   ..$ vjust     : NULL
##   ..$ angle     : NULL
##   ..$ lineheight: NULL
##   ..$ margin    :Classes 'margin', 'unit'  atomic [1:4] 0 0 7.2 0
##   .. .. ..- attr(*, "valid.unit")= int 8
##   .. .. ..- attr(*, "unit")= chr "pt"
##   ..$ debug     : NULL
##   ..- attr(*, "class")= chr [1:2] "element_text" "element"
##  $ plot.margin          :Classes 'margin', 'unit'  atomic [1:4] 6 6 6 6
##   .. ..- attr(*, "valid.unit")= int 8
##   .. ..- attr(*, "unit")= chr "pt"
##  - attr(*, "class")= chr [1:2] "theme" "gg"
##  - attr(*, "complete")= logi TRUE
##  - attr(*, "validate")= logi TRUE

You can change this for an individual plot

qplot(carat, price, data = diamonds) +
    ggtitle("Price vs Carat for Diamonds")

You can make your own theme, or modify an existing one.

Themes are made up of elements which can be one of:

• element_line
• element_text
• element_rect
• element_blank

This gives you a lot of control over plot appearance.

• Axis: axis.line, axis.text.x, axis.text.y, axis.ticks, axis.title.x, axis.title.y
• Legend: legend.background, legend.key, legend.text, legend.title
• Panel: panel.background, panel.border, panel.grid.major, panel.grid.minor
• Strip: strip.background, strip.text.x, strip.text.y

p <- qplot(carat, price, data = diamonds) + 
    ggtitle("Price vs Carat for Diamonds")
p + theme(plot.title = element_text(colour = "red", angle = 45))

We could also choose to remove all axes (helpful for maps):

p + theme(
    axis.text.x = element_blank(),
    axis.text.y = element_blank(),
    axis.title.x = element_blank(),
    axis.title.y = element_blank(),
    axis.ticks.length = unit(0, "cm")
)

The ggsave() function will automatically save the last plot produced:

qplot(price, carat, data = diamonds)

ggsave("diamonds.png")
ggsave("diamonds.pdf")
ggsave("diamonds.png", width = 6, height = 6)

We can also explicitly tell it which plot to save:

dplot <- qplot(carat, price, data = diamonds)
ggsave("diamonds.png", plot = dplot, dpi = 72)

1. Save a pdf of a scatterplot of price vs carat
2. Open up the pdf in Adobe Acrobat (or another PDF Reader)
3. Save a png of the same scatterplot