The spruce data frame has 1027 rows and 6 columns. The data
consists of measurements on 79 sitka spruce trees over two growing
seasons. The trees were grown in four controlled environment chambers,
of which the first two, containing 27 trees each, were treated with
introduced ozone at 70 ppb whilst the remaining two, containing 12 and
13 trees, were controls.
Usage
data(spruce)
Format
This data frame contains the following columns:
chamber
a numeric vector of chamber numbers
ozone
a factor with levels enriched and normal
id
a numeric vector of tree id
time
a numeric vector of the time when the measurements were
taken, measured in days since Jan. 1, 1988
wave
a numeric vector of the measurement number
logsize
a numeric vector of the log-size
Source
Diggle, P.J., Liang, K.Y., and Zeger, S.L. (1994) Analysis of Longitudinal
Data, Clarendon Press.