All credits to this answer, I only did some messy adjustments. Adding xpd=NA allows you to draw outside of the plot:
# function to draw curly braces
# x, y position where to put the braces
# range is the length of the brace
# position: 1 vertical, 2 horizontal
# direction: 1 left/down, 2 right/up
# depth controls width of the shape
CurlyBraces <- function(x0, x1, y0, y1, pos = 1, direction = 1, depth = 1) {
a=c(1,2,3,48,50) # set flexion point for spline
b=c(0,.2,.28,.7,.8) # set depth for spline flexion point
curve = spline(a, b, n = 50, method = "natural")$y * depth
curve = c(curve,rev(curve))
if (pos == 1){
a_sequence = seq(x0,x1,length=100)
b_sequence = seq(y0,y1,length=100)
}
if (pos == 2){
b_sequence = seq(x0,x1,length=100)
a_sequence = seq(y0,y1,length=100)
}
# direction
if(direction==1)
a_sequence = a_sequence+curve
if(direction==2)
a_sequence = a_sequence-curve
# pos
if(pos==1)
lines(a_sequence,b_sequence, lwd=1.5, xpd=NA) # vertical
if(pos==2)
lines(b_sequence,a_sequence, lwd=1.5, xpd=NA) # horizontal
}
windows(width=5, height=5)
par(oma=c(2,0,0,2))
plot(c(),c(), xlim=c(0,11), ylim=c(0,11), xlab='')
# horizontal brace
CurlyBraces(x0=2, x1=8, y0=-3, y1=-3, pos = 2, direction = 2, depth=1.5)
# vertical brace
CurlyBraces(x0=12, x1=12, y0=2, y1=6, pos = 1, direction = 1, depth=0.5)
