Add titles, footnotes, page Number, and a bounding box to a grid grob

This function is useful to label grid grobs (also ggplot2, and lattice plots) with title, footnote, and page numbers.

decorate_grob(
  grob,
  titles,
  footnotes,
  page = "",
  width_titles = grid::unit(1, "npc"),
  width_footnotes = grid::unit(1, "npc"),
  border = TRUE,
  padding = grid::unit(rep(1, 4), "lines"),
  margins = grid::unit(c(1, 0, 1, 0), "lines"),
  outer_margins = grid::unit(c(2, 1.5, 3, 1.5), "cm"),
  gp_titles = grid::gpar(),
  gp_footnotes = grid::gpar(fontsize = 8),
  name = NULL,
  gp = grid::gpar(),
  vp = NULL
)

Arguments

grob: (grob)
a grid grob object, optionally NULL if only a grob with the decoration should be shown.
titles: (character)
titles given as a vector of strings that are each separated by a newline and wrapped according to the page width.
footnotes: (character)
footnotes. Uses the same formatting rules as titles.
page: (string or NULL)
page numeration. If NULL then no page number is displayed.
width_titles: (grid::unit)
width of titles. Usually defined as all the available space grid::unit(1, "npc"), it is affected by the parameter outer_margins. Right margins (outer_margins[4]) need to be subtracted to the allowed width.
width_footnotes: (grid::unit)
width of footnotes. Same default and margin correction as width_titles.
border: (flag)
whether a border should be drawn around the plot or not.
padding: (grid::unit)
padding. A unit object of length 4. Innermost margin between the plot (grob) and, possibly, the border of the plot. Usually expressed in 4 identical values (usually "lines"). It defaults to grid::unit(rep(1, 4), "lines").
margins: (grid::unit)
margins. A unit object of length 4. Margins between the plot and the other elements in the list (e.g. titles, plot, and footers). This is usually expressed in 4 "lines", where the lateral ones are 0s, while top and bottom are 1s. It defaults to grid::unit(c(1, 0, 1, 0), "lines").
outer_margins: (grid::unit)
outer margins. A unit object of length 4. It defines the general margin of the plot, considering also decorations like titles, footnotes, and page numbers. It defaults to grid::unit(c(2, 1.5, 3, 1.5), "cm").
gp_titles: (gpar)
a gpar object. Mainly used to set different "fontsize".
gp_footnotes: (gpar)
a gpar object. Mainly used to set different "fontsize".
name: a character identifier for the grob. Used to find the grob on the display list and/or as a child of another grob.
gp: A "gpar" object, typically the output from a call to the function gpar. This is basically a list of graphical parameter settings.
vp: a viewport object (or NULL).

Value

A grid grob (gTree).

Details

The titles and footnotes will be ragged, i.e. each title will be wrapped individually.

Examples

library(grid)

titles <- c(
  "Edgar Anderson's Iris Data",
  paste(
    "This famous (Fisher's or Anderson's) iris data set gives the measurements",
    "in centimeters of the variables sepal length and width and petal length",
    "and width, respectively, for 50 flowers from each of 3 species of iris."
  )
)

footnotes <- c(
  "The species are Iris setosa, versicolor, and virginica.",
  paste(
    "iris is a data frame with 150 cases (rows) and 5 variables (columns) named",
    "Sepal.Length, Sepal.Width, Petal.Length, Petal.Width, and Species."
  )
)

## empty plot
grid.newpage()

grid.draw(
  decorate_grob(
    NULL,
    titles = titles,
    footnotes = footnotes,
    page = "Page 4 of 10"
  )
)


# grid
p <- gTree(
  children = gList(
    rectGrob(),
    xaxisGrob(),
    yaxisGrob(),
    textGrob("Sepal.Length", y = unit(-4, "lines")),
    textGrob("Petal.Length", x = unit(-3.5, "lines"), rot = 90),
    pointsGrob(iris$Sepal.Length, iris$Petal.Length, gp = gpar(col = iris$Species), pch = 16)
  ),
  vp = vpStack(plotViewport(), dataViewport(xData = iris$Sepal.Length, yData = iris$Petal.Length))
)
grid.newpage()
grid.draw(p)


grid.newpage()
grid.draw(
  decorate_grob(
    grob = p,
    titles = titles,
    footnotes = footnotes,
    page = "Page 6 of 129"
  )
)


## with ggplot2
library(ggplot2)

p_gg <- ggplot2::ggplot(iris, aes(Sepal.Length, Sepal.Width, col = Species)) +
  ggplot2::geom_point()
p_gg

p <- ggplotGrob(p_gg)
grid.newpage()
grid.draw(
  decorate_grob(
    grob = p,
    titles = titles,
    footnotes = footnotes,
    page = "Page 6 of 129"
  )
)


## with lattice
library(lattice)

xyplot(Sepal.Length ~ Petal.Length, data = iris, col = iris$Species)

p <- grid.grab()

grid.newpage()
grid.draw(
  decorate_grob(
    grob = p,
    titles = titles,
    footnotes = footnotes,
    page = "Page 6 of 129"
  )
)


# with gridExtra - no borders
library(gridExtra)
#> 
#> Attaching package: ‘gridExtra’
#> The following object is masked from ‘package:dplyr’:
#> 
#>     combine
grid.newpage()
grid.draw(
  decorate_grob(
    tableGrob(
      head(mtcars)
    ),
    titles = "title",
    footnotes = "footnote",
    border = FALSE
  )
)