plot with broken y-axis

Here is a function to implement broken y-axis.
Several enhancements could be done to make it nicer but it works. However it was not fully tested.




plot.break <- function(x, y, at.cut, at.continue, add.cut, 
                       number.ticks.bottom, number.ticks.up, 
                       min.y, max.y, ...) {
  
  p.plot <- list(...)
  p.plot <- modifyList(list(x = x, y=ifelse(y>at.cut, y-at.continue+add.cut, y),
                            bty="n", type="p", las=1,
                            ylim=c(min.y, max.y-at.continue+add.cut), 
                            yaxt="n", xlab="x", ylab="y"), 
                       p.plot)
  do.call(plot, p.plot)
  y.axis <- c(seq(from=0, to=at.cut, length=number.ticks.bottom), 
              seq(from=at.cut+add.cut, to=ScalePreviousPlot()$ylim[2], 
                  length=number.ticks.up))
  axis(2, at=y.axis,
       labels=ifelse(y.axis>at.cut, y.axis+at.continue-add.cut, y.axis), 
       las=1)
  par(xpd=TRUE)
  
  x.left <- ScalePreviousPlot()$xlim[1]-0.05*ScalePreviousPlot()$xlim["range"]
  x.right <- ScalePreviousPlot()$xlim[1]+0.00*ScalePreviousPlot()$xlim["range"]
  
  polygon(x=c(x.left, x.right, x.right, x.left, x.left), 
          y=c(at.cut+0.5, at.cut+0.5, at.cut+add.cut-0.5, 
              at.cut+add.cut-0.5, at.cut+0.5), 
          col="white", border=NA)
}

x <- 1:10
y <- c(rnorm(5, 10, 5), rnorm(5, 100, 5))

library(HelpersMG)
at.cut <- 20
at.continue <- 60
add.cut <- 5
number.ticks.bottom <- 3
number.ticks.up <- 5
min.y <- 0
max.y <- 120

plot.break(x = x, y=y, at.cut= 20,
           at.continue= 60,
           add.cut= 5,
           number.ticks.bottom= 3,
           number.ticks.up= 5,
           min.y= 0,
           max.y= 120, xlab="Value x")