[R] Lattice xyplot

[Duncan Mackay]

In addition to Berts comments

Once you change the order you change the non factored  id' ordering. If you make it a factor it may be  easier to see what is going on
I think I have copied correctly - see the differences 

# original data
xyplot(y ~ time, data=dat, groups=id, aspect = "fill", type = c("p", "l"),  xlab = "Time", ylab = "Y")
# order
dat2<-dat[order(dat$id, dat$time),]
xyplot(y ~ time, data=dat2, groups=id, aspect = "fill", type = c("p", "l"),  xlab = "Time", ylab = "Y")
# make ID a factor
dat3 <- dat1
xyplot(y ~ time, data=dat3, groups=id, aspect = "fill", type = c("p", "l"),  xlab = "Time", ylab = "Y")
# ordered + ID a factor
dat4 <- dat3
dat4<-dat[order(dat4$id, dat4$time),]
xyplot(y ~ time, data=dat4, groups=id, aspect = "fill", type = c("p", "l"),  xlab = "Time", ylab = "Y")

Regards

Duncan

Duncan Mackay
Department of Agronomy and Soil Science
University of New England
Armidale NSW 2351
Email: home: mackay at northnet.com.au

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of array chip via R-help
Sent: Monday, 1 May 2017 11:07
To: r-help at r-project.org
Subject: [R] Lattice xyplot

Dear all, I am new to lattice, so would appreciate anyone's help on the questions below. I am using xyplot to plot some trend in my dataset. Using the example dataset attached, I am trying to plot variable "y" over variable "time" for each subject "id":
dat<-read.table("dat.txt",sep='\t',header=T,row.names=NULL)
xyplot(y ~ time, data=dat, groups=id, aspect = "fill", type = c("p", "l"),  xlab = "Time", ylab = "Y")

It appears that it just worked fine. But if I sort the "dat" first, the plot will look somewhat different!
dat<-dat[order(dat$id, dat$time),]xyplot(y ~ time, data=dat, groups=id, aspect = "fill", type = c("p", "l"),  xlab = "Time", ylab = "Y")
Why is that? Do you need to sort the data first before using xyplot? Why xyplot can not understand the dataset unless it is sorted first?
Thanks,
John