Creating line plot with time scale and labels in r - r

Question

I am trying to create the plot like following (many times I end up drawing a plot like this by hand, but this time I want to plot it myself).
Here is my data and my trial:
myd <- data.frame (period = c("Triassic", "Jurasic",
"Cretaceous", "Cenzoic"), myears = c(245, 208, 145, 65),
label = c(226, 176,105, 32 ))
myd2 <- data.frame (event = c("Diansaurs_strt", "Birds",
"Diansaurs_ext", "Human"), myears = c(235, 200, 60, 0.5))
myd2$x <- -0.25
with (myd2, plot(x,myears,ylim=c(0,250),
xlim = c(0, 10), axes=F,xlab="",ylab="",type="p",pch=17))
with (myd2,text(x,myears,event,pos=4,xpd=T))
axis(side=2,at = myd$label, labels = myd$period)
I have issues particularly matching of axis with plot and orientation of text and points. Any other idea or improvement help appreciated.

Answer 1

For constructing novel plots "from the ground up", and for maximal control over individual graphical elements, the grid graphical system is hard to beat:
library(grid)
## Set up plotting area with reasonable x-y limits
## and a "native" scale related to the scale of the data.
x <- -1:1
y <- extendrange(c(myd$myears, myd2$myears))
dvp <- dataViewport(x, y, name = "figure")
grid.newpage()
pushViewport(dvp)
## Plot the central timeline
grid.lines(unit(0, "native"), unit(c(0,245), "native"),
gp = gpar(col="dodgerblue"))
## Annotate LHS
grid.segments(x0=0.5, x1=0.47,
y0=unit(c(0, myd$myears), "native"),
y1=unit(c(0, myd$myears), "native"),
gp=gpar(col="dodgerblue"))
grid.text(label=c(0, myd$myears), x=0.44, y=unit(c(0, myd$myears), "native"))
grid.text(label=myd$period, x=0.3, y=unit(myd$label, "native"),
just=0, gp=gpar(col="dodgerblue", fontface="italic"))
## Annotate RHS
## Create a function that plots a pointer to the specified coordinate
pointer <- function(x, y, width=1) {
grid.polygon(x = x + unit(width*(c(0, .1, .1)), "npc"),
y = y + unit(width*(c(0, .03, -.03)), "npc"),
gp = gpar(fill="dodgerblue", col="blue", lwd=2))
}
## Call it once for each milestone
for(y in myd2$myears) {
pointer(unit(.5, "npc"), y=unit(y, "native"), width=0.3)
}
## Or, if you just want blue line segments instead of those gaudy pointers:
## grid.segments(x0=0.5, x1=0.53,
## y0=unit(c(myd2$myears), "native"),
## y1=unit(c(myd2$myears), "native"), gp=gpar(col="dodgerblue"))
grid.text(label=myd2$event, x=0.55, y=unit(myd2$myears, "native"),
just=0)

Answer 2

You can try something like this to get you started:
myd <- data.frame(period = c("", "Triassic", "Jurasic",
"Cretaceous", "Cenzoic", ""),
myears = c(260, 245, 208, 145, 65, -5),
label = c(260, 226, 176,105, 32, -5))
myd2 <- data.frame(event = c("Dinosaurs_strt", "Birds",
"Dinosaurs_ext", "Human"),
myears = c(235, 200, 60, 0.5))
myd2$x <- 1
with(myd2, plot(x, myears, ylim = c(-5, 250), xlim = c(0, 10),
axes = FALSE, xlab = "", ylab = "", type = "n"))
with(myd2, text(x, myears, event, pos = 4, xpd = TRUE))
axis(side = 2, at = myd$label, labels = myd$period, las = 2)
X0 <- rep(myd2$x, 4)
Y0 <- myd2$myears
X1 <- rep(-.25, 4)
Y1 <- Y0
arrows(X0, Y0, X1, Y1)
I've added an extra empty element at the start and end of your data in "myd" to help with the axis. Then, instead of using pch, I've used arrows to match the right hand labels with the axis.
Some tweaking could probably make it look a lot nicer.

Answer 3

Here are some enhancements ( I suggest to add 0 for now just to make scale well):
myd <- data.frame (period = c("Triassic", "Jurasic",
"Cretaceous", "Cenzoic", "now"), myears = c(245, 208, 145, 65, 0),
label = c(226, 176,105, 32, NA ))
myd2 <- data.frame (event = c("Diansaurs_strt", "Birds", "Diansaurs_ext", "Human"),
myears = c(235, 200, 60, 0.5))
myd2$x <- -0.25
with (myd2, plot(x,myears,ylim=c(0,250), xlim = c(0, 10),
axes=F,xlab="",ylab="",type="p",pch=17, col = "green"))
with (myd2, plot(x,myears,ylim=c(0,250),
xlim = c(0, 10), axes=F,xlab="",ylab="",type="p",pch="-", col = "green"))
with (myd2,text(x,myears,event,pos=4,xpd=T), col = "green")
axis(side=2,at = myd$label, labels = myd$period, tick = FALSE,
las = 2, col = "green", )
axis(side=2,at = myd$myears, labels = myd$myears, las = 2, col = "green")
There are few issues remaining you might want to change oriantation of the arrow (I belief that you can someway find <- symbol, but I do not know how to).

Answer 4

For drawing the triangles look at the my.symbols and ms.polygon functions in the TeachingDemos package.
In your right graph above the Dinosaurs are moved up, if you want this in general (moving labels that would otherwise be too close or overlap) then look at the spread.labs function in the TeachingDemos package.
Some other possible functions that could help with the plot are text, mtext, grconvertX, grconvertY, segments, and axis.