[R] align two lattice plots with grid

[Deepayan Sarkar]

On Mon, Dec 1, 2008 at 8:13 AM, baptiste auguie <ba208 at exeter.ac.uk> wrote:
> Dear list,
>
> I need to align two plots on top of each other for comparison (they only
> have the x-axis in common). When the y-labels have a different extent, I
> cannot find a way to align the x-axes, as illustrated below,
>
>
>> library(grid)
>> library(lattice)
>> x <- seq(0, 10, length=100)
>> y <- sin(x)
>> y2 <- 10*sin(x)
>> f <- rep(c("1", "2"), each=50)
>>
>> p1 <- xyplot(y~x,groups=f, ylab="BIG LABEL",
>> # auto.key=list(space="right"),
>> par.settings = list(layout.width = list(panel=1,  ylab = 2, axis.left
>> =1.0, left.padding=1,
>>        ylab.axis.padding=1, axis.panel=1)))
>>
>> p2 <- xyplot(y2~x, ylab="a",
>> par.settings = list(layout.width = list(panel=1,  ylab = 2, axis.left
>> =1.0, left.padding=1,
>>        ylab.axis.padding=1, axis.panel=1)))
>>
>> pushViewport(viewport(layout=grid.layout(nrow = 2, ncol = 1 ,
>>                                                widths=unit(6, "inches"),
>>                           heights=unit(c(3, 2), "inches"))))
>>
>> pushViewport(viewport(layout.pos.col=1, layout.pos.row=1, just="center",
>> name = "top"))
>>
>> print(p1, newpage=F, panel.width=list(4, "inches"),
>> panel.height=list(2.5, "inches"))
>> upViewport()
>> pushViewport(viewport(layout.pos.col=1, layout.pos.row=2, just="center",
>> name = "bottom"))
>>
>> print(p2, newpage=F, panel.width=list(4, "inches"),
>> panel.height=list(1.5, "inches"))
>> upViewport()


The most transparent approach is to manipulate your data into a
suitable format; here's a crude first attempt:

xyplot(c(y2, y) ~ c(x, x) | gl(2, 100),
       groups = rep(c("1", "2"), c(150, 50)),
       scales = list(y = "free"),
       layout = c(1, 2), strip = FALSE)


In general, the latticeExtra package has some tools to combine
arbitrary trellis objects (thanks to Felix Andrews):

library(latticeExtra)

update(c(p2, p1, x.same = TRUE),
       layout = c(1, 2),
       ylab = list(c("a", "BIG LABEL"), y = c(1/6, 2/3)),
       par.settings = list(layout.heights = list(panel = c(1, 2))))

-Deepayan