Combining 3 different matrix plots in R - r

Question

Can anyone tell me how to create a plot which features 3 different matrices sets of data. In general, I have 3 different matricies of data all 1*1001 dimensions, and i wish to plot all 3 on the same graph.
I have managed to get one matrix to plot at once, and assemble the code to create the other 2 matrices but not to plot it. B[i,] is randomly generated data. What I would like to know is what would be the coding to get all 3 plots together on one graph.
Code for one matrix:
ntime<-1000
average.price.at.each.timestep<-matrix(0,nrow=1,ncol=ntime+1)
for(i in 1:(ntime+1)){
average.price.at.each.timestep[i]<-mean(B[i,])
}
matplot(t, t(average.price.at.each.timestep), type="l", lty=1, main="MC Price of a Zero Coupon Bond", ylab="Price", xlab = "Option Exercise Date")
Code for 3:
average.price.at.each.timestep<-matrix(0,nrow=1,ncol=ntime+1)
s.e.at.each.time <-matrix(0,nrow=1,ncol=ntime+1)
upper.c.l.at <- matrix(0,nrow=1,ncol=ntime+1)
lower.c.l.at <- matrix(0,nrow=1,ncol=ntime+1)
std <- function(x) sd(x)/sqrt(length(x))
for(i in 1:(ntime+1)){
average.price.at.each.timestep[i]<-mean(B[i,])
s.e.at.each.time[i] <- std(B[i,])
upper.c.l.at[i] <- average.price.at.each.timestep[i]+1.96*s.e.at.each.time[i]
lower.c.l.at[i] <- average.price.at.each.timestep[i]-1.96*s.e.at.each.time[i]
}
I'm still struggling with this as I cannot get the solutions given to match with my data sets, I have now included the code below that generates the matrix B as a working example so you can see the data I am dealing with. As you can see it produces a plot of the different prices, I would like a plot with the average price and confidence intervals of the average.
# Define Bond Price Parameters
#
P<-1 #par value
# Define Vasicek Model Parameters
#
rev.rate<-0.3 #speed of reversion
long.term.mean<-0.1 #long term level of the mean
sigma<-0.05 #volatility
r0<-0.03 #spot interest rate
Strike<-0.05
# Define Simulation Parameters
#
T<-50 #time to expiry
ntime<-1000 #number of timesteps
yearstep<-ntime/T #yearstep
npaths<-1000 #number of paths
dt<-T/ntime #timestep
R <- matrix(0,nrow=ntime+1,ncol=npaths) #matrix of Vasicek interest rate values
B <- matrix(0,nrow=ntime+1,ncol=npaths) # matrix of Bond Prices
R[1,]<-r0 #specifies that all paths start at specified spot rate
B[1,]<-P
# do loop which generates values to fill matrix R with multiple paths of Interest Rates as they evolve over time.
# stochastic process based on standard normal distribution
for (j in 1:npaths) {
for (i in 1:ntime) {
dZ <-rnorm(1,mean=0,sd=1)*sqrt(dt)
Rij<-R[i,j]
Bij<-B[i,j]
dr <-rev.rate*(long.term.mean-Rij)*dt+sigma*dZ
R[i+1,j]<-Rij+dr
B[i+1,j]<-Bij*exp(-R[i+1,j]*dt)
}
}
t<-seq(0,T,dt)
par(mfcol = c(3,3))
matplot(t, B[,1:pmin(20,npaths)], type="l", lty=1, main="Price of a Zero Coupon Bond", ylab="Price", xlab = "Time to Expiry")

Answer 1

Your example isn't reproducible, so I created some fake data that I hope is structured similarly to yours. If this isn't what you were looking for, let me know and I'll update as needed.
# Fake data
ntime <- 100
mat1 <- matrix(rnorm(ntime+1, 10, 2), nrow=1, ncol=ntime+1)
mat2 <- matrix(rnorm(ntime+1, 20, 2), nrow=1, ncol=ntime+1)
mat3 <- matrix(rnorm(ntime+1, 30, 2), nrow=1, ncol=ntime+1)
matplot(1:(ntime+1), t(mat1), type="l", lty=1, ylim=c(0, max(c(mat1,mat2,mat3))),
main="MC Price of a Zero Coupon Bond",
ylab="Price", xlab = "Option Exercise Date")
# Add lines for mat2 and mat3
lines(1:101, mat2, col="red")
lines(1:101, mat3, col="blue")
UPDATE: Is this what you're trying to do?
matplot(t, t(average.price.at.each.timestep), type="l", lty=1,
main="MC Price of a Zero Coupon Bond", ylab="Price",
xlab = "Option Exercise Date")
matlines(t, t(upper.c.l.at), lty=2, col="red")
matlines(t, t(lower.c.l.at), lty=2, col="green")
See plot below. If you have multiple columns that you want to plot (as in your updated example where you plot 20 separate paths) and you want to add lower and upper CIs for all of them (though this would make the plot unreadable), just use a matrix of upper and lower CI values that correspond to each path in average.price.at.each.timestep and use matlines to add them to your existing plot of the multiple paths.

Answer 2

This is doable using ggplot2 and reshape2. The structures you have are a little awkward, which you could improve by using a data frame instead of a matrix.
#Dummy data
average.price.at.each.timestep <- rnorm(1000, sd=0.01)
s.e.at.each.time <- rnorm(1000, sd=0.0005, mean=1)
#CIs (note you can vectorise this):
upper.c.l.at <- average.price.at.each.timestep+1.96*s.e.at.each.time
lower.c.l.at <- average.price.at.each.timestep-1.96*s.e.at.each.time
#create a data frame:
prices <- data.frame(time = 1:length(average.price.at.each.timestep), price=average.price.at.each.timestep, upperCI= upper.c.l.at, lowerCI= lower.c.l.at)
library(reshape2)
#turn the data frame into time, variable, value triplets
prices.t <- melt(prices, id.vars=c("time"))
#plot
library(ggplot2)
ggplot(prices.t, aes(time, value, colour=variable)) + geom_line()
This produces the following plot:
This can be improved somewhat by using geom_ribbon instead:
ggplot(prices, aes(time, price)) + geom_ribbon(aes(ymin=lowerCI, ymax=upperCI), alpha=0.1) + geom_line()
Which produces this plot:

Answer 3

Here's another, slightly different ggplot solution that does not require you to calculate the confidence limits first - ggplot does it for you.
# create sample dataset
set.seed(1) # for reproducible example
B <- matrix(rnorm(1000,mean=rep(10+1:10/2,each=10)),nc=10)
library(ggplot2)
library(reshape2) # for melt(...)
gg <- melt(data.frame(date=1:nrow(B),B), id="date")
ggplot(gg, aes(x=date,y=value)) +
stat_summary(fun.y = mean, geom="line")+
stat_summary(fun.y = function(y)mean(y)-1.96*sd(y)/sqrt(length(y)), geom="line",linetype="dotted", color="blue")+
stat_summary(fun.y = function(y)mean(y)+1.96*sd(y)/sqrt(length(y)), geom="line",linetype="dotted", color="blue")+
theme_bw()
stat_summary(...) summarizes the y-values for a given value of x (the date). So in the first call, it calculates the mean, in the second the lowerCL, and in the third the upperCL.
You could also create a CL(...) function, and call that:
CL <- function(x,level=0.95,type=c("lower","upper")) {
fact <- c(lower=-1,upper=1)
mean(x) - fact[type]*qnorm((1-level)/2)*sd(x)/sqrt(length(x))
}
ggplot(gg, aes(x=date,y=value)) +
stat_summary(fun.y = mean, geom="line")+
stat_summary(fun.y = CL, type="lower", geom="line",linetype="dotted", color="blue")+
stat_summary(fun.y = CL, type="upper", geom="line",linetype="dotted", color="blue")+
theme_bw()
This produces a plot identical to the one above.