Adding annotation to R plots with layout - r

Question

I am plotting multiple panels of variable size in R, and using layout to accomplish this. I, however, would like to add arrows and text between the plots but seem to, in my best attempts using arrow and text functions, have the annotations being cut-off at the end of the axis I'm plotting on.
MWE:
circle <- function(){
theta <- seq(from = 0, to = 2*pi - pi/1000, by = 2*pi/1000)
x <- cos(theta)
y <- sin(theta)
circ <- list(x, y)
}
shape_plot <- function(xs, ys, typ){
plot(xs, ys, type=typ, axes=FALSE, xlab='', ylab='', asp=1, lwd=4)
}
sample1 <- function(data, n){
pts <- sort(floor(runif(n, min=1, max=1000)))
xs <- data[[1]]
x <- xs[pts] + .1*runif(n, min=-1, max=1)
x <- c(x, x[1])
ys <- data[[2]]
y <- ys[pts] + .1*runif(n, min=-1, max=1)
y <- c(y, y[1])
samp <- list(x, y)
}
layout(matrix(c(1,2, 1,3, 1,4), 3, 2, byrow = TRUE))
circ <- circle()
shape_plot(circ[[1]], circ[[2]], 'l')
label <- rep('circle', 3)
for (i in 1:3){
samp <- sample1(circ, 50)
shape_plot(samp[[1]], samp[[2]], 'p')
}
This returns the following figure:
What I would like is something like this (but less ugly, and not created in GIMP):
Thanks!

Answer 1

In response to a comment by #rawr, I came up with the following modifications which enabled me to accomplish this goal:
...
layout(matrix(c(1,2, 1,3, 1,4), 3, 2, byrow = TRUE))
par(xpd=NA)
...
...
arrows(x0=1.5, x1=2.5, y0=1, y1=2, length=0.1, lwd = lweight)
arrows(x0=1.5, x1=2.5, y0=0, y1=0, length=0.1, lwd = lweight)
arrows(x0=1.5, x1=2.5, y0=-1, y1=-2, length=0.1, lwd = lweight)
text(x=1.8, y=1.8, expression('s'[1]^'a'), cex=2)
text(x=1.8, y=0.3, expression('s'[2]^'a'), cex=2)
text(x=1.8, y=-1.8, expression('s'[3]^'a'), cex=2)
...
Result:

Answer 2

Using layout seemed to cause problems.
Below is a modified version of your MWE that I think does what you are looking for.
circle <- function(){
theta <- seq(from = 0, to = 2*pi - pi/1000, by = 2*pi/1000)
x <- cos(theta)
y <- sin(theta)
circ <- data.frame(x, y)
}
shape_plot <- function(xs, ys, typ){
plot(xs, ys, type=typ, axes=FALSE, xlab='', ylab='', asp=1, lwd=4)
}
sample1 <- function(data, n){
pts <- sort(floor(runif(n, min=1, max=1000)))
xs <- data[[1]]
x <- xs[pts] + .1*runif(n, min=-1, max=1)
x <- c(x, x[1])
ys <- data[[2]]
y <- ys[pts] + .1*runif(n, min=-1, max=1)
y <- c(y, y[1])
samp <- data.frame(x, y)
}
circ <- circle()
shape_plot(circ[[1]], circ[[2]], 'l')
label <- rep('circle', 3)
samp <- list()
nudge <- cbind(5,c(3,0,-3))
for (i in 1:3){
s <- sample1(circ, 50)
samp[[i]] <- t(apply(s, 1, function(x) x + nudge[i,]))
}
samp <- Reduce(rbind, samp)
tot <- rbind(circ, samp)
shape_plot(tot[[1]], tot[[2]], typ = 'n')
points(circ, type = 'l')
points(samp, type = 'p')
arrows(1.2,1,3.7,2.5)
arrows(1.2,0,3.7,0)
arrows(1.2,-1,3.7,-2.5)
text(2.5,2, label = "arrow 1", srt = atan(1/1.5)*180/pi)
text(2.5,0.25, label = "arrow 2")
text(2.5,-2, label = "arrow 3", srt = atan(-1/1.5)*180/pi)