R plot heatmap of matrix with superposed line - r

Question

I have a matrix whose values I want to plot. Using the image function it looks like this.
How can I plot a line over the image?
(In my case, it want to plot a line over the maximum values along the x axes)
Edit
The image and the line I want to plot over are the output from the Bayesian Online Changepoint detection. Since it is quite short I'll share the whole code. The plotting part is at the end:
# Bayesian Online Changepoint Detection
# Adams, MacKay 2007
# http://hips.seas.harvard.edu/content/bayesian-online-changepoint-detection
#######################################
# Other python and matlab implementations
# https://github.com/JackKelly/bayesianchangepoint
# http://hips.seas.harvard.edu/content/bayesian-online-changepoint-detection
# http://www.inference.phy.cam.ac.uk/rpa23/cp/gaussdemo.m
# http://www.inference.phy.cam.ac.uk/rpa23/cp/studentpdf.m
# http://www.inference.phy.cam.ac.uk/rpa23/cp/constant_hazard.m
# Even more commented, but different paper:
# https://github.com/davyfeng/ipdata/blob/master/csv/bocpd/core/bocpd.m
# Generate data
x1 <- rnorm(100, 10.5, 0.1)
x2 <- rnorm(100, 1, 0.1)
x3 <- rnorm(100, -10, 0.1)
x4 <- rnorm(100, -1, 0.1)
x5 <- rnorm(100, 5, 0.1)
x6 <- rnorm(30, 1, 0.1)
x7 <- rnorm(100, 8, 0.1)
x <- c(x1,x2,x3,x4,x5, x6,x7)
##############
# Algorithm
##############
# Prepare the scaled and shifted student-t
dt.scaled.shifted <- function(x, m, s, df) stats::dt((x-m)/s, df)/s
# Prepare the Hazard function
hazard <-function(x, lambda=200){rep(1/lambda, length(x))}
L <- length(x)
R <- matrix(rep(0,(L+1)*(L+1)), L+1, L+1)
R[1,1] <- 1 # for t=1 where are sure that p(r=1)=1
mu0 <- 0; kappa0 <- 1; alpha0 <-1; beta0 <- 1;
muT <- mu0
kappaT <- kappa0
alphaT <- alpha0
betaT <- beta0
maxes <- rep(0, L)
# Process data as they come in
for(t in 1:L){
# Evaluate predictive probability
predprobs <- dt.scaled.shifted(x[t], muT, betaT*(kappaT+1)/(alphaT*-kappaT), 2*alphaT)
H <- hazard(x[1:t])
# Calculate growth probabilities
R[2:(t+1), t+1] <- R[1:t,t]*predprobs*(1-H)
# Calculate changepoint (reset) probabilities
R[1,t+1] <- sum(R[1:t,t]*predprobs*H)
# Renormalize
R[,t+1] <- R[,t+1] / sum(R[,t+1])
# Update parameters for each possible run length
# keep the past ones since they will be used iteratively
muT0 <- c(mu0, (kappaT*muT + x[t])/(kappaT+1))
kappaT0 <- c(kappa0,kappaT+1)
alphaT0 <- c(alpha0, alphaT + 0.5)
betaT0 <- c(beta0, kappaT + (kappaT * (x[t]-muT)^2)/(2*(kappaT+1)))
muT <- muT0
kappaT <- kappaT0
alphaT <- alphaT0
betaT <- betaT0
# Store the maximum, to plot later
maxes[t] <- which.max(R[,t])
}
# Plot results
par(mfrow=c(2,1))
plot(x, type='l')
image((-t(log(R))), col = grey(seq(0,1,length=256)), axes=T)
par(new=T)
plot(1:(dim(R)[1]-1), maxes,type='l', col="red")
On the top there is the original data. On the bottom, the probability of a current run to have length y. The red line on the bottom should fit the dark shades.

Answer 1

(to be deleted. It does not work. I leave it temporaly to save the comments.)
I got it, I thought I had already tried par(new=T) but obviously I hadn't:
m <- matrix(rnorm(100,1,1),50,50)
image(m, col = grey(seq(0,1,length=256)))
par(new=T)
plot(seq(0,1, length=50), type='l', col="red", lwd=5)
Quick example simulating the whole process:
data <- vector()
for(i in 1:50){
data <- rbind(data, dpois(1:50, i^1.2))
}
maxes <- apply(data, 1, which.max)
image(-data, col = grey(seq(0,1,length=256)))
par(new=T)
plot(1:dim(data)[1], c(maxes),type='l')