| sitka {SemiPar} | R Documentation |
Sitka spruce data
Description
The sitka data frame contains measurements
of log-size for 79 Sitka spruce trees grown in normal
or ozone-enriched environments. Within each year, the
data are organised in four blocks, corresponding to
four controlled environment chambers. The first
two chambers, containing 27 trees each, have
an ozone-enriched atmosphere, the remaining two,
containing 12 and 13 trees respectively, have a normal
(control) atmosphere.
Usage
data(sitka)Format
This data frame contains the following columns:
- id.num
identification number of tree.
- order
time order ranking within each tree.
- days
time in days since 1st January, 1988.
- log.size
tree size measured on a logarithmic scale.
- ozone
indicator ozone treatment: 0=control,1=ozone.
Source
Diggle, P.J., Heagerty, P., Liang, K.-Y. and Zeger, S.L. (2002). Analysis of Longitudinal Data, Second Edition, Oxord: Oxford University Press.
References
Ruppert, D., Wand, M.P. and Carroll, R.J. (2003)
Semiparametric Regression Cambridge University Press.
http://stat.tamu.edu/~carroll/semiregbook/
Examples
library(SemiPar)
data(sitka)
attach(sitka)
library(lattice)
ozone.char <- rep("control",nrow(sitka))
ozone.char[ozone==1] <- "ozone"
xyplot(log.size~days|ozone.char,data=sitka,groups=id.num,type="b")