Annotation: log tick marks

This annotation adds log tick marks with diminishing spacing. These tick marks probably make sense only for base 10.

annotation_logticks(
  base = 10,
  sides = "bl",
  outside = FALSE,
  scaled = TRUE,
  short = unit(0.1, "cm"),
  mid = unit(0.2, "cm"),
  long = unit(0.3, "cm"),
  colour = "black",
  size = 0.5,
  linetype = 1,
  alpha = 1,
  color = NULL,
  ...
)

Arguments

base: the base of the log (default 10)
sides: a string that controls which sides of the plot the log ticks appear on. It can be set to a string containing any of "trbl", for top, right, bottom, and left.
outside: logical that controls whether to move the log ticks outside of the plot area. Default is off (FALSE). You will also need to use coord_cartesian(clip = "off"). See examples.
scaled: is the data already log-scaled? This should be TRUE (default) when the data is already transformed with log10() or when using scale_y_log10(). It should be FALSE when using coord_trans(y = "log10").
short: a grid::unit() object specifying the length of the short tick marks
mid: a grid::unit() object specifying the length of the middle tick marks. In base 10, these are the "5" ticks.
long: a grid::unit() object specifying the length of the long tick marks. In base 10, these are the "1" (or "10") ticks.
colour: Colour of the tick marks.
size: Thickness of tick marks, in mm.
linetype: Linetype of tick marks (solid, dashed, etc.)
alpha: The transparency of the tick marks.
color: An alias for colour.
...: Other parameters passed on to the layer

Examples

# Make a log-log plot (without log ticks)
a <- ggplot(msleep, aes(bodywt, brainwt)) +
 geom_point(na.rm = TRUE) +
 scale_x_log10(
   breaks = scales::trans_breaks("log10", function(x) 10^x),
   labels = scales::trans_format("log10", scales::math_format(10^.x))
 ) +
 scale_y_log10(
   breaks = scales::trans_breaks("log10", function(x) 10^x),
   labels = scales::trans_format("log10", scales::math_format(10^.x))
 ) +
 theme_bw()

a + annotation_logticks()                # Default: log ticks on bottom and left

a + annotation_logticks(sides = "lr")    # Log ticks for y, on left and right

a + annotation_logticks(sides = "trbl")  # All four sides


a + annotation_logticks(sides = "lr", outside = TRUE) +
 coord_cartesian(clip = "off")  # Ticks outside plot


# Hide the minor grid lines because they don't align with the ticks
a + annotation_logticks(sides = "trbl") + theme(panel.grid.minor = element_blank())


# Another way to get the same results as 'a' above: log-transform the data before
# plotting it. Also hide the minor grid lines.
b <- ggplot(msleep, aes(log10(bodywt), log10(brainwt))) +
 geom_point(na.rm = TRUE) +
 scale_x_continuous(name = "body", labels = scales::math_format(10^.x)) +
 scale_y_continuous(name = "brain", labels = scales::math_format(10^.x)) +
 theme_bw() + theme(panel.grid.minor = element_blank())

b + annotation_logticks()


# Using a coordinate transform requires scaled = FALSE
t <- ggplot(msleep, aes(bodywt, brainwt)) +
  geom_point() +
  coord_trans(x = "log10", y = "log10") +
  theme_bw()
t + annotation_logticks(scaled = FALSE)
#> Warning: Removed 27 rows containing missing values (geom_point).


# Change the length of the ticks
a + annotation_logticks(
  short = unit(.5,"mm"),
  mid = unit(3,"mm"),
  long = unit(4,"mm")
)

Arguments

See also

Examples