The ggdiagram package takes an object-oriented approach to making diagrams and plots the results using ggplot2.
My motivation in making ggdiagram was to find a way to approach the functionality of TikZ but with the flexibility and convenience of R. The ggdiagram package is built atop S7 and is integrated with ggplot2, making heavy use of ggtext, ggforce, and ggarrow.
The ggdiagram package is not a replacement for the standard ggplot2
functions. The underlying grammar of ggplot2 is well designed for
visualizing data. The ggdiagram functions are best suited for creating a
small number of visual objects that interrelate. If anything, they can
be thought of as extensions of ggplot2::annotate.
You can install ggdiagram from R-universe like so:
install.packages("ggdiagram", repos = "https://wjschne.r-universe.dev")Assuming the remotes package is already installed, you can install the development version of ggdiagram like so:
remotes::install_github("wjschne/ggdiagram")In Figure 1, we create a
circle object with ob_circle and a rectangle object with
ob_rectangle, placing the rectangle such that there is .5 units of
separation between the two objects.
The ggdiagram function is a a wrapper for ggplot, that sets some
defaults (e.g., theme_void, coord_equal, fonts, line size, etc.).
The ob_* functions have methods such that they can be added to any
ggplot. Under the hood, they are first converted to an appropriate geom
and then added to the ggplot object. In this case, an ob_circle is
converted to a ggforce:geom_circle, and an ob_rectangle is converted
to a ggforce::geom_shape.
The connect function connects the circle and rectangle at their edges
with an arrow (drawn with ggarrow::geom_arrow_segment).
library(ggdiagram)
c1 <- ob_circle(radius = 1 / sqrt(pi))
r2 <- ob_rectangle() |>
place(from = c1,
where = "right",
sep = .5)
ggdiagram() +
c1 +
r2 +
connect(c1, r2, resect = 1) 
Figure 1: Connecting a circle and a square with an arrow.