[R] define colors for groups in lattice xyplot

[Chris Campbell]

Hi Geert

###

dataset <- data.frame ( time = rep(1:5,times=9),
                genotype = factor(rep(rep
(c("A","B","C"),each=5),times=3 )),
                location= factor(rep (paste("LOC",1:3),each=15)),
                color = rep (rep
(c("red","green","blue"),each=5),times=3
),
                result = rnorm (45))

library(lattice)

# The black, red, green behaviour you were seeing is because 
# dataset$color is a factor
dataset$color
# which is coded 1, 2, 3 levels = ("red", "green", "blue").
# This is being interpreted as the first three colours of the palette
pallete()

# coerce the vector to a character vector
as.character(dataset$color)

# gives you
xyplot( result ~ time | location, data=dataset,groups=genotype,
                fill.color = as.character(dataset$color),
                panel = function(x, y,fill.color,...,subscripts) {
                        fill = fill.color [subscripts]
                        panel.xyplot(x, y,pch=19, col=fill, type ="b")}
)

# Lines only take a single value so only the first value of the vector, 
# "red", is passed to line colour.

# these are simple alternatives

xyplot( result ~ time | location, data=dataset, groups=genotype,
pch=c(1,2,3),                            		type="b",
col=c("red","blue","green"))
 
xyplot( result ~ time | location, data=dataset, groups=genotype,
pch=c(1,2,3),                            		type="b",
col=dataset$color)

# or use

par.settings <- list(superpose.symbol = list(col = c("red", "green",
"blue"), fill = c("red", "green", "blue")), superpose.line = list(col =
c("red", "green", "blue")) )

xyplot( result ~ time | location, data=dataset,groups=genotype,pch=19,
type = "b", par.settings = par.settings)

###

Hope this helps

Chris


###
Hadley Wickham, Creator of ggplot2 - teaching in the UK. 1st - 2nd
November 2010. 
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Chris Campbell

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-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of geert.demeyer at bayercropscience.com
Sent: 03 September 2010 07:44
To: r-help at r-project.org
Subject: [R] define colors for groups in lattice xyplot

Dear all,

Lattice provides automatic coloring for subgroups on each panel by the 
simple use of a groups statement. For an application I want to change 
these colors to a predifined set. This works well using a panel function

in stead of the default as long as there are only points in the graphs. 
When I set type="b" things get messed up. Any idea why? I include sample

code for illustration below.

Thanks for your ideas.

Geert

dataset <- data.frame ( time = rep(1:5,times=9),
                genotype = factor(rep(rep
(c("A","B","C"),each=5),times=3
)),
                location= factor(rep (paste("LOC",1:3),each=15)),
                color = rep (rep
(c("red","green","blue"),each=5),times=3
),
                result = rnorm (45))

library(lattice)

xyplot( result ~ time | location, data=dataset,groups=genotype,pch=19, 
type="b")

xyplot( result ~ time | location, data=dataset,groups=genotype,
                fill.color = dataset$color,
                panel = function(x, y,fill.color,...,subscripts) {
                        fill = fill.color [subscripts]
                        panel.xyplot(x, y,pch=19, col=fill)}
)

xyplot( result ~ time | location, data=dataset,groups=genotype,
                fill.color = dataset$color,
                panel = function(x, y,fill.color,...,subscripts) {
                        fill = fill.color [subscripts]
                        panel.xyplot(x, y,pch=19, col=fill, type ="b")}
)
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