xyplot with lowess curves

I haven't had much luck with a custom panel function; mainly because I
don't truly understand how to embedd the functionality into the xyplot
command.

Here's a reproducible example if you can help out.

Thanks,
Dave

library (lattice)

d <- NULL
models <- c('A','B','C','D')
n = 100
for (i in seq(along = models)){
 d <- rbind(
   d, data.frame (
     Model = models[i],
     Year = seq(1960, length.out=n, by = 1),
     SnowLineElevation = runif(n, 0, 100)
   )
 )
}

xyplot (
 SnowLineElevation ~ Year | Model,
 data = d,
 ylim = c(0,100),
 type = c('p','smooth'),
 col = 'blue',
 pch = 21,
 xlab = 'Year',
 ylab = 'Snowline Elevation [m]'
)

-----Original Message-----
From: Sundar Dorai-Raj [mailto:sdorairaj at gmail.com]
Sent: Monday, February 02, 2009 11:43 AM
To: Hutchinson,David [PYR]
Cc: r-help at r-project.org
Subject: Re: [R] xyplot with lowess curves

You'll need a custom panel function. It would also help if you provided
a reproducible example:

xyplot (
 SnowLineElevation ~ Year | Model,
 data = data,
 panel = function(x, y, col, ...) {
   col <- ifelse(panel.number() == 1, "red", "green")
   panel.xyplot(x, y, col = "blue", ...)
   panel.loess(x, y, col = col)
 },
 ylim = c(0,1800),
 pch = 21,
 xlab = 'Year',
 ylab = 'Snowline Elevation [m]'
)

Alternatively, you can use the group argument in conjunction with the
panels:

xyplot(SnowLineElevation ~ Year | Model, data, groups = Model, type =
c("p", "smooth"))

if you want the points and the lines to be the same color.

--sundar

On Mon, Feb 2, 2009 at 10:20 AM, Hutchinson,David [PYR]
<David.Hutchinson at ec.gc.ca> wrote:

I am trying to change the attributes of the lowess lines fit to an
xyplot command, but have been unsuccessful in my search of the online
help. Right now, both the points and lowess line come out in the same
color (blue). I am unsure how I can change the properties of the
lowess line separately.

xyplot (
 SnowLineElevation ~ Year | Model,
 data = data,
 ylim = c(0,1800),
 type = c('p','smooth'),
 col = 'blue',
 pch = 21,
 xlab = 'Year',
 ylab = 'Snowline Elevation [m]'
)

Any help would be much appreciated,

Dave

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