Text boxes and decorations

Colors

The background and border colors of slides can be changed by setting their col, border, and lwd arguments:

slide(col = pal_seeblau[[1]], border = Petrol, lwd = 5)  # set colors of slide background and border

slide(col = pal_peach[[2]], border = NA)  # colored slide without a border

Similarly, the background color of xboxes can be changed by the col argument:

xbox(col = Pinky)  # set background color of xbox

Dimensions

By default, both slide and xbox fill the entire plotting region (i.e., all margins are set to 0).

The width of a slide is set to 4/3 of its height (of 1). To change this default, use the dim argument for specifying the slide’s x- and y-dimensions, respectively:

slide(dim = c(3, 1))  # a slide 3 times wider than high

Note that changes in slide dimensions are invisible when viewing images interactively, as R automatically scales images to the size of the canvass. They mostly affect the relation between metrics when adding elements to an object.

Similarly, an xbox has the default dimensions of a unit square (i.e., dim = c(1, 1)). To change this default, use the dim argument for specifying the xbox’s x- and y-dimensions, respectively:

xbox(col = Petrol, dim  = c(1, 2))  # an xbox 2 times higher than wide

The two strokes of the X (in the top right corner) are orthogonal when viewing the xbox at the aspect ratio indicated by dim (i.e., here: at a ratio of width x = 1 to height y = 2). When viewing the box at any different aspect ratio, the X appears to be distorted. Hence, viewing and printing plots at the desired aspect ratio helps when creating an xbox.

Mark text

The mark() function allows highlighting text by plotting it with colored background boxes (to provide the functionality of “Markieren”):

By default, mark() assumes that we want to add highlighted text to an existing plot. The text labels to be added are provided (as a character vector) by the labels argument, their coordinates as the corresponding x and y arguments. Various text decorations (i.e., text and background colors, text sizes, and font types) can be set by specifying additional arguments (i.e., col, col_bg, cex, and font, respectively):

# Some pre-existing plot: 
n <- 20
set.seed(1)
par(mar = c(0, 0, 0, 0))
plot(x = runif(n), y = runif(n), type = "p", pch = 16, cex = 20, col = grey(0, .2),
     axes = FALSE, xlab = "", ylab = "")

# Add 1 marked label:
mark(labels = "Some messy plot", x = .02, y = .9)

# Add 2 more marked labels:
mark(labels = c("Note something here.", "More highlighting here."), 
     x = c(.1, .6), y = c(.2, .4),
     col_bg = c(pal_seeblau[[2]], pal_peach[[3]]), cex = 1.2)

If no pre-existing plot is available, setting the new_plot argument to either "blank" or "slide" will generate a new default plot (by calling the slide() function described above):

# A sentence to plot: 
s <- c("Markieren",
       "ist ein Bestandteil",
       "von Studieren.")

# Create a new plot (of type "slide"):
mark(labels = s,
     x = 0, y = .85, y_layout = .03,
     col_bg = Seeblau,
     cex = 1.5,
     new_plot = "slide")

# Add text to the same plot:
mark(labels = s,
     x = 0, y = .40, y_layout = .03,
     col_bg = pal_pinky[[2]],
     cex = 1.5, 
     new_plot = "none")

Rather than providing explicit x and y coordinates for all text elements in labels, the calls above defined an initial coordinate and used a numeric y_layout argument to fix the distance between consecutive text labels (to a value of .03).

As an alternative to numeric coordinates and position values, x_layout and y_layout also accept some special values (as character strings):

1. x_layout accepts:

   • x_layout = "center" for centering labels horizontally (on the first label or the middle),
     
   • x_layout = "left" left-justifies labels (on the first label or the middle), and
     
   • x_layout = "right" right-justifies labels (on the first label or the middle).

2. y_layout accepts:

   • y_layout = "even" for an even distribution of labels across the available y-space, and
     
   • y_layout = "flush" to omit space between adjacent labels (as in y_layout = 0).

Thus, the position and orientation of the text labels can be controlled by using the x_layout and y_layout options:

See ?mark for details.

Underline text

The uline() function allows emphasizing text by plotting it with colored underlining (to provide the functionality of “Unterstreichen”):

As with mark() above, the uline() command distinguishes between creating a new plot (by setting new_plot to either "blank" or “slide”) or adding to a pre-existing plot (by using the default new_plot = "none"):

lbl_uline <- c("This is neat, true, and terribly important")
uline(labels = lbl_uline, new_plot = "blank", y = .6, cex = 1.1)  # create a new plot
uline(labels = "(which is why we underline it).", y = .45, cex = 1)  # add to plot

The arguments for text elements (labels), text positions (x, y, y_layout), and text properties and decorations (col, col_bg, cex, and font) work as they do for mark(). For instance, shorter vectors are recycled to match the length of labels:

slogan <- c("Geradlinig", "Farbenfroh", "Beweglich", "Bunt", "Paradiesisch")
uline(labels = slogan,
      x = c(0, .5), y = .9, y_layout = "even",
      col = c("black", Bordeaux), col_bg = c(Seeblau, Seegruen), 
      cex = 1.1, font = 2, new_plot = "blank")

The position and orientation of the text labels can be controlled by using the x_layout and y_layout options:

Post text

The post() function allows adding text to a rectangular xbox (to provide the functionality of “Merken”):

By default, post() assumes a pre-existing xbox to which the text elements of labels are to be added.
For square boxes, setting new_plot to "xbox" creates a new xbox with its default dimensions of dim = c(1, 1).
By adjusting its color and text arguments, post() allows creating simple badges or logos:

# Badge (to view as 250 x 250 pixel):
post(labels = "ToDo", y = .35, 
     col = "white", col_bg = pal_signal[[1]],
     cex = 3, font = 2, new_plot = "xbox")  

# Badge (to view as 250 x 250 pixel):
post(labels = "R", y = .35, 
     col = "white", col_bg = pal_seeblau[[5]],
     cex = 8, font = 2, new_plot = "xbox")

Another potential use of post() is for creating images providing contact details:

address <- c("Dr. B. F. Skinner", " ",
             "Department of Psychology",
             "Office Z101",
             "Tel.: +49 7531 88-0815",
             "Fax: +49 7531 88-0810",
             "b.f.skin@uni-konstanz.de")

post(labels = "Contact",
     y = .7,
     cex = 1.2, font = 2,
     col_bg = Petrol,
     new_plot = "xbox")  # create new plot 

post(labels = address,
     y = .5, y_layout = .03,
     new_plot = "none")  # add to plot

As above, the position and orientation of the text labels can be controlled by using the x_layout and y_layout options:

Headings

The heading() function makes it easy to create recognizable headings:

By default, the function creates a new slide (i.e., new_plot = "slide") and positions the text elements of labels on its left edge (i.e., x = 0, y = .8 and y_layout = "flush"). Headings violating the recommendations (see p. 25 of the CD manual) will generate a message, for instance:

# Beware of step-wise arrangements:
heading(labels = c("Ich", "bin keine", "gute Headline."))
#> Step-wise titles are discouraged: Consider re-arranging?

# To avoid warning:
heading(labels = c("Ich bin", "eine alternative", "Headline."))

When colors are left unspecified, heading() selects colors that are appropriate for the number of elements in labels (i.e., shades of Seeblau for col_bg = "default"). However, default colors can be overwritten by setting the col and col_bg arguments:

heading(labels = c("Ene,", "mene, miste,", "es rappelt", "in der Kiste."), 
        col = "white", col_bg = c(Pinky, Seegruen, Bordeaux, Karpfenblau))

URLs

One of the more obscure rules (on p. 31 of the CD manual) concerns the rendering of URLs, in which typical web patterns (like “http” or “www”) are to be omitted and replaced by a typographical dash (which is longer than a hyphen). The url_unikn utility function allows formatting URLs the uni.kn way:

my_url <- url_unikn("https://www.uni-konstanz.de/")  # input URL as copied from web browser
my_url  # formatted URL
#> [1] "‒ uni-konstanz.de"

# Put URL at bottom of an xbox:
post(labels = my_url, x = .05, y = .1, font = 4, 
     col_bg = pal_seeblau[[5]], new_plot = "xbox")