Offset axis guide with minor ticks

This guide draws the axis only as wide as the outermost tick marks, similar to offset axes from Prism. It also adds minor ticks.

guide_prism_offset_minor(
  title = waiver(),
  check.overlap = FALSE,
  angle = NULL,
  n.dodge = 1,
  order = 0,
  position = waiver()
)

Arguments

title

A character string or expression indicating a title of guide. If NULL, the title is not shown. By default (waiver()), the name of the scale object or the name specified in labs() is used for the title.

check.overlap

silently remove overlapping labels, (recursively) prioritizing the first, last, and middle labels.

angle

Compared to setting the angle in theme() / element_text(), this also uses some heuristics to automatically pick the hjust and vjust that you probably want. Can be one of the following:

• NULL to take the angles and hjust/vjust directly from the theme.

• waiver() to allow reasonable defaults in special cases.

• A number representing the text angle in degrees.

n.dodge

The number of rows (for vertical axes) or columns (for horizontal axes) that should be used to render the labels. This is useful for displaying labels that would otherwise overlap.

order

A positive integer of length 1 that specifies the order of this guide among multiple guides. This controls in which order guides are merged if there are multiple guides for the same position. If 0 (default), the order is determined by a secret algorithm.

position

Where this guide should be drawn: one of top, bottom, left, or right.

Value

Returns a prism_offset_minor guide class object.

Details

Control the length of the axis by adjusting the breaks argument in scale_(x|y)_continuous() or scale_(x|y)_discrete(). Similarly, the number of minor ticks can be changed using the minor_breaks argument.

Control the length of minor ticks by setting prism.ticks.length to a unit object using theme, for example: prism.ticks.length = unit(2, "pt"). The major tick lengths are adjusted using the standard axis.ticks.length.

Examples

library(ggplot2)

## base plot
base <- ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  theme(axis.line = element_line(colour = "black"))

## add minor ticks to x and y axes
base +
  scale_x_continuous(
    limits = c(0, 6),
    guide = "prism_offset_minor"
  ) +
  scale_y_continuous(
    limits = c(10, 35),
    guide = "prism_offset_minor"
  )


## you can also use the guides function to add minor ticks
base +
  guides(x = "prism_offset_minor", y = "prism_offset_minor")


## adjust number of minor ticks by adjusting minor breaks
base +
  scale_x_continuous(
    limits = c(0, 6),
    minor_breaks = seq(0, 6, 0.5),
    guide = "prism_offset_minor"
  ) +
  scale_y_continuous(
    limits = c(10, 35),
    minor_breaks = seq(10, 35, 1.25),
    guide = "prism_offset_minor"
  )


## adjust the length of major ticks with the usual axis.ticks.length element
base +
  scale_x_continuous(
    limits = c(0, 6),
    minor_breaks = seq(0, 6, 0.5),
    guide = "prism_offset_minor"
  ) +
  scale_y_continuous(
    limits = c(10, 35),
    minor_breaks = seq(10, 35, 1.25),
    guide = "prism_offset_minor"
  ) +
  theme(
    axis.ticks.length = unit(10, "pt")
  )


## adjust the length of minor ticks with a new prism.ticks.length element
base +
  scale_x_continuous(
    limits = c(0, 6),
    minor_breaks = seq(0, 6, 0.5),
    guide = "prism_offset_minor"
  ) +
  scale_y_continuous(
    limits = c(10, 35),
    minor_breaks = seq(10, 35, 1.25),
    guide = "prism_offset_minor"
  ) +
  theme(
    axis.ticks.length = unit(10, "pt"),
    prism.ticks.length = unit(5, "pt")
  )


## to get log10 minor ticks just use a log10 scale and set the minor breaks
ggplot(msleep, aes(bodywt, brainwt)) +
  geom_point(na.rm = TRUE) +
  scale_x_log10(limits = c(1e0, 1e4),
                minor_breaks = rep(1:9, 4)*(10^rep(0:3, each = 9)),
                guide = "prism_offset_minor") +
  theme(axis.line = element_line(colour = "black"))


## change colour and tick length with the usual elements
base +
  scale_x_continuous(
    limits = c(0, 6),
    minor_breaks = seq(0, 6, 0.5),
    guide = "prism_offset_minor"
  ) +
  scale_y_continuous(
    limits = c(10, 35),
    minor_breaks = seq(10, 35, 1.25),
    guide = "prism_offset_minor"
  ) +
  theme(
    axis.ticks.length = unit(10, "pt"),
    prism.ticks.length = unit(5, "pt"),
    axis.ticks = element_line(colour = "red"),
    axis.line = element_line(colour = "blue")
  )