[R] xyplot() with segments() superposed?

[Yuelin Li]

In the hypothetical example below, how do I add two segments() into
the two panels, respectively?  Say segments(x0=5, y0=10, x1=5, y1=20)
on the left and segments(x0=15, y0=-10, x1=15, y1=-2) on the right?
Many thanks in advance,

Yuelin Li.

ps. part of the code came from a solution given by Deepayan Sarkar.

-------------------
library(lattice)
set.seed(12345)
x <- 0:20
y.male.obs <- - 1.2 * x + 22 + rnorm(length(x), sd = 3)
y.male.prd <- - 1.2 * x + 22
y.fema.obs <- - 2.2 * x + 30 + rnorm(length(x), sd = 2)
y.fema.prd <- - 2.2 * x + 30
tdat <- data.frame(x = rep(x, 8), 
        y = rep(c(y.male.obs, y.male.prd, y.fema.obs, y.fema.prd), 2),
        sex = rep(rep(c("m", "f"), each = 2*length(x)), 2), 
        cohort = rep(c("1970", "1980"), each = 4*length(x)), 
        source = rep(rep(c("obs", "prd"), each = length(x)), 4)  )
xyplot(y ~ x | as.factor(cohort), data = tdat, 
       groups = interaction(sex, source), 
       type = c("p", "p", "l", "l"), distribute.type = TRUE)

 
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