Add straight lines to a plot

Description

These functions add straight line(s) through the current plot.

Usage

type_abline(a = 0, b = 1)

type_hline(h = 0)

type_vline(v = 0)

Arguments

a, b	the intercept (default: a = 0) and slope (default: b = 1) terms. Numerics of length 1 or equal to the number of facets.
h	y-value(s) for horizontal line(s). Numeric of length 1 or equal to the number of facets.
v	x-value(s) for vertical line(s). Numeric of length 1 or equal to the number of facets.

Details

Unlike most tinyplot types, type_abline, type_hline, and type_vline cannot be called as a base plot layer. Instead they must called as a subsequent layer via tinyplot_add.

Examples

library("tinyplot")

#
## abline

tinyplot(x = -10:10, y = rnorm(21) + -10:10, grid = TRUE)
tinyplot_add(type = "abline")
# same as...
# tinyplot_add(type = type_abline(a = 0, b = 1))

# customize by passing bespoke intercept and slope values
tinyplot_add(type = type_abline(a = -1, b = -0.5))

#
## hline and vline

# Base plot layer
tinyplot(mpg ~ hp | cyl, facet = "by", data = mtcars, ylim = c(0, 40))

# Add horizontal lines at the (default) 0 y-intercept
tinyplot_add(type = "hline", col = "grey")

# Note that group+facet aesthetics will be inherited. We can use this to
# add customized lines (here: the mean `mpg` for each `cyl` group)  
tinyplot_add(type = type_hline(with(mtcars, tapply(mpg, cyl, mean))), lty = 2)

# Similar idea for vline
tinyplot_add(type = type_vline(with(mtcars, tapply(hp, cyl, mean))), lty = 2)