Marc Bernard wrote:

> Dear all,

>

> I have created the following data (that you can run) in order to explain my problem:

>

> y <- rep(c(1,2), 8)

> id <- rep(1:8,each=2)

> x1 <- rep(c("-a","+a"), each = 8)

> x2 <- rep(c("-b","+b"), each = 2, times = 4)

> x3 <- rep(c("-c", "+c"), each = 4,2)

> df <- data.frame(cbind(id,y,x1,x2,x3))

>

> If I do:

>

> xyplot(y~ x3|x1*x2,data=df,groups=id,type = "b")

>

> then my id's are joined by lines which is what I want. However when I wanted to add an horizontal line for each panel by using "panel.abline" the lines disapears, i.e.

>

> xyplot(y~ x3|x1*x2,data=df,groups=id,type = "b",panel=function(x,y)

> {

> panel.xyplot(x,y)

> panel.abline(h=1.5)

> }

> )

>

>

> I would be grateful if someone can tell me how can I correct the second statement in order to have horizontal lines for each panel and each id are joined by lines.

>

> Thank you,

>

> Bernard,

This appears to work for me.

xyplot(y~ x3|x1*x2,data=df,groups=id,type = "b",

panel=function(x,y,groups,...) {

panel.superpose(x,y,groups,...)

panel.abline(h=1.5)})

--

Kevin E. Thorpe

Biostatistician/Trialist, Knowledge Translation Program

Assistant Professor, Department of Public Health Sciences

Faculty of Medicine, University of Toronto

email:

[hidden email] Tel: 416.946.8081 Fax: 416.946.3297

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