# [R] Grid Points

Gabor Grothendieck ggrothendieck at gmail.com
Sun Aug 20 15:28:30 CEST 2006

```Try this.  gl(2,50) is such that the first 50 points are series 1
and the second 50 points are series 2.  The scales= argument
defines the positions of the tick marks and the xlim= argument
defines the x axis limits.  The layout puts the panels on top
of each other rather than side by side.  strip = FALSE eliminates
the strip above each panel.  type= says we want lines.  The
panel function puts points at the grid locations in each panel
and then calls xyplot to plot the lines.

library(lattice)
library(grid)

x <- 601:700
at <- seq(500, 800, 50)
xyplot(x ~ x | gl(2, 50), scales = list(at = at), xlim = c(500, 700),
layout = 1:2, strip = FALSE, type = "l",
panel = function(...) {
grid.points(at, unit(rep(.01, length(at)), "npc"),
pch = 20, size = unit(.2, "char"))
panel.xyplot(...)
})

On 8/20/06, Anupam Tyagi <AnupTyagi at yahoo.com> wrote:
> How do I put grid points (not grid lines) as the base layer of an xyplot?
>
> Is there a way to vary the interval at which x and y grid points are placed?
>
> Is it possible to start a graph so that Y axis begins at 500 and ends at 800? I
> am only interested in focusing on the relative distance between the points whose
> values are between 500 and 800, but not their relative distance from zero.
>
> Is there a way in R to draw two graphs so that that "share" the same X axis, but
> without the gap that mfrow() creates? The origin of the top graph should be
> where the Y-axis of the bottom graph ends. It will be useful for what I am
> trying to do to have the X axis of the top graph be invisible.
>
> Anupam.
>
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