Multiple data points in one R ggplot2 plot

Question

I have two sets of data points that both relate to the same primary axis, but who differ in secondary axis. Is there some way to plot them on top of each other in R using ggplot2?

What I am looking for is basically something that looks like this:

4+           |
 | x       . + 220
3+     . .   |
 |   x       |
2+   .       + 210
 |     x     |
1+ .     x x |
 |           + 200
0+-+-+-+-+-+-+
     time   

   . temperatur
   x car sale

(This is just a example of possible data)

Answer 1

I'm not an expert on this, but it's my understanding that this is possible with lattice, but not with ggplot2. See this leanr blog post for an example of a secondary axis plot. Also see Hadley's response to this question.

Here's an example of how to do it in lattice (from Gabor Grothendieck):

library(lattice)
library(grid)  # needed for grid.text

# data

Lines.raw <- "Date  Fo  Co
6/27/2007  57.1  13.9
6/28/2007  57.7  14.3
6/29/2007  57.8  14.3
6/30/2007  57  13.9
7/1/2007  57.1  13.9
7/2/2007  57.2  14.0
7/3/2007  57.3  14.1
7/4/2007  57.6  14.2
7/5/2007  58  14.4
7/6/2007  58.1  14.5
7/7/2007  58.2  14.6
7/8/2007  58.4  14.7
7/9/2007    58.7 14.8
"

# in reality next stmt would be DF <- read.table("myfile.dat", header = TRUE)
DF <- read.table(textConnection(Lines.raw), header = TRUE)
DF$Date <- as.Date(DF$Date, "%m/%d/%Y")

par.settings <- list(
        layout.widths = list(left.padding = 10, right.padding = 10),
        layout.heights = list(bottom.padding = 10, top.padding = 10)
)

xyplot(Co ~ Date, DF, default.scales = list(y = list(relation = "free")),
        ylab = "C", par.settings = par.settings)

trellis.focus("panel", 1, 1, clip.off = TRUE)
  pr <- pretty(DF$Fo)
  at <- 5/9 * (pr - 32)
  panel.axis("right", at = at, lab = pr, outside = TRUE)
  grid.text("F", x = 1.1, rot = 90) # right y axis label
trellis.unfocus()