Plotting line segments on top of a plot from a previous run of an R function

Question

I have an R function called stock (below). I was wondering if it might be in any way possible that the result of each run of the function (which is a plot() ) be plotted (ie, added) on top of the plot from the previous run of the function? (the picture below the code may show this)

stock = function(m, s){

 loop = length(s) 

 I = matrix(NA, loop, 2)

for(i in 1:loop){
I[i,] = quantile(rbeta(1e2, m, s[i]), c(.025, .975))
 }
plot(rep(1:loop, 2), I[, 1:2], ty = "n", ylim = 0:1, xlim = c(1, loop))

segments(1:loop, I[, 1], 1:loop, I[, 2])
}
# Example of use:
stock(m = 2, s = c(1, 10, 15, 20, 25, 30))
stock(m = 50, s = c(1, 10, 15, 20, 25, 30)) #The result of this run be plotted on top of previous run above

Answer 1

Simplest would be to add an argument for the option. As segments() by default adds to the previous frame, all you have to do is to not do a new plot() .

stock = function(m, s, add=FALSE) {

    loop = length(s) 
    I = matrix(NA, loop, 2)

    for(i in 1:loop) {
        I[i,] = quantile(rbeta(1e2, m, s[i]), c(.025, .975))
    }
    if (!add) {
        plot(rep(1:loop, 2), I[, 1:2], ty = "n", ylim = 0:1, xlim = c(1, loop))
    }
    segments(1:loop, I[, 1], 1:loop, I[, 2], xpd = NA)
}

# Example of use:
set.seed(1)
stock(m = 2, s = c(1, 10, 15, 20, 25, 30))
stock(m = 50, s = seq(1, 90, 10), add=TRUE)