Compute the area on graph of time series - database

Question

My problem is that I want to compute some specific area inside of graph of time series.
This is the graph :
an this is the code how I generate my time series :
x1<-rnorm(250,0.4,0.9)
x <- as.matrix(x1)
t <- ts(x[,1], start=c(1,1), frequency=30)
plot(t,xlim=c(2,4),main="Daily closing price of Walterenergie",ylab="Adjusted close Returns",xlab="Times",col="blue")
abline(0,0)
So my question is how to compute the area in green and then how to compute the area in red separately.
If you need the cothe for the graph :
###### Graph of the performance of my portfolio
num.points <- 250
x.vals <- 1:num.points
values <- x1
plot(x.vals, values, t="l", pch=20, main="Daily closing price", xlab="Times", ylab="Adjusted close Returns", las=1)
abline(h=0, col="darkgray", lwd=2)
crossings <- values[-length(values)] * values[-1]
crossings <- which(crossings < 0)
# You can draw the points to check (uncomment following line)
# points(x.vals[crossings], values[crossings], col="red", pch="X")
intersections <- NULL
for (cr in crossings)
{
new.int <- cr + abs(values[cr])/(abs(values[cr])+abs(values[cr+1]))
intersections <- c(intersections, new.int)
}
# Again, let's check the intersections
#points(intersections, rep(0, length(intersections)), pch=20, col="red", cex=0.7)
last.intersection <- 0
for (i in intersections)
{
ids <- which(x.vals<=i & x.vals>last.intersection)
poly.x <- c(last.intersection, x.vals[ids], i)
poly.y <- c(0, values[ids], 0)
if (max(poly.y) > 0)
{
col="green"
}
else
{
col="red"
}
polygon(x=poly.x, y=poly.y, col=col)
last.intersection <- i
}