Drawing a flametree in Excalidraw

Let’s add a flametree into Excalidraw.

The R object

The flametree package uses ggplot2 for drawing, so we can piggyback the aesthetic mapping and simply extract point coordinates and colours in the plot’s data.

library(minixcali)
library(flametree)
library(ggplot2)

dat <- flametree_grow(seed = 4, time = 5) # data structure
img <- flametree_plot(data = dat) # ggplot object
img

gb <- ggplot_build(img)

tr <- gb$data[[1]]
b <- split(tr, tr$group)
str(b, list.len = 3)

## List of 63
##  $ 1 :'data.frame':  100 obs. of  11 variables:
##   ..$ colour   : chr [1:100] "#1E2640" "#1E2640" "#1E2640" "#1E2640" ...
##   ..$ size     : num [1:100] 4.67 4.67 4.67 4.67 4.67 ...
##   ..$ x        : num [1:100] -0.43 -0.43 -0.43 -0.43 -0.43 ...
##   .. [list output truncated]
##  $ 2 :'data.frame':  100 obs. of  11 variables:
##   ..$ colour   : chr [1:100] "#E2A766" "#E2A766" "#1E2640" "#1E2640" ...
##   ..$ size     : num [1:100] 1.28 1.28 4.67 4.67 4.67 ...
##   ..$ x        : num [1:100] -0.389 -0.389 -0.389 -0.39 -0.39 ...
##   .. [list output truncated]
##  $ 3 :'data.frame':  100 obs. of  11 variables:
##   ..$ colour   : chr [1:100] "#E2A766" "#E2A766" "#1E2640" "#1E2640" ...
##   ..$ size     : num [1:100] 1.28 1.28 4.67 4.67 4.67 ...
##   ..$ x        : num [1:100] -0.992 -0.995 -0.998 -1.001 -1.005 ...
##   .. [list output truncated]
##   [list output truncated]

From there it’s a relatively straight-forward process to add one branch at a time to the Excalidraw tree.

d <- Excali_doc()


library(scales)

scale <- 100

for (ii in seq_along(b)) {
  s <- b[[ii]]
  
  r_x <- range(s$x)
  r_y <- range(s$y)
  
  m <- scale * cbind(s$x - r_x[1],-s$y - r_y[1])
  
  shape <- xkd_draw(
    x = scale * r_x[1],
    y =  scale * r_y[1],
    width = scale * diff(r_x),
    height = scale * diff(r_y),
    strokeWidth = 1,
    roughness = 0L,
    strokeSharpness = "round",
    groupIds = list("levelplot", paste0('level-', ii)),
    fillStyle = "solid",
    strokeColor = s$colour[1],
    backgroundColor = s$colour[1],
    points = m)
  
  d$add(shape)
  
}

d$export('tree.json')

You can see this drawing at: https://excalidraw.com/#json=5730260331003904,U-jtojw6AHcRuH_lw2P4ng

(with time=7 the tree is more interesting but Excalidraw struggles and doesn’t offer a shareable link)

Baptiste Auguié

2024-03-31

The R object