R Lattice Plot Multiple Lines with Specific Color

Question

I have two problems that I am having trouble to solve for. Firstly when I do a multiple column matrix plot using lattice xyplot , I find that all the points are connected. How can I get separate disconnected lines?

x<-cbind(rnorm(10),rnorm(10))
xyplot(x~1:nrow(x),type="l")

Secondly, I am having trouble figuring out how to make one line thicker than the other. For example, given that I want column 1, then column 1's line will be thicker than that of column 2.

Answer 1

The lattice plotting paradigm,like that of ggplot2 that followed it, expects data to be in long format in dataframes:

dfrm <- data.frame( y=c(rnorm(10),rnorm(10)),
                    x=1:10, 
                    grp=rep(c("a","b"),each=10))
xyplot(y~x, group=grp, type="l", data=dfrm, col=c("red","blue"))

Answer 2

This might not be the most elegant solution but it gets the job done:

x<-cbind(rnorm(10),rnorm(10))
plot1<-xyplot(x[,1]~1:nrow(x),type="l",col="red",lwd=3)
plot2<-xyplot(x[,2]~1:nrow(x),type="l")

library(latticeExtra)
plot1+plot2

I assumed that you wanted V1 and V2 plotted against the number of observations. Otherwise you indeed only have one line. You can adjust the axis and labels according to taste.