On this Picostat.com statistics page, you will find information about the spruce data set which pertains to Log-size of 79 Sitka spruce trees. The spruce data set is found in the geepack R package. You can load the spruce data set in R by issuing the following command at the console data("spruce"). This will load the data into a variable called spruce. If R says the spruce data set is not found, you can try installing the package by issuing this command install.packages("geepack") and then attempt to reload the data. If you need to download R, you can go to the R project website. You can download a CSV (comma separated values) version of the spruce R data set. The size of this file is about 27,221 bytes.

Log-size of 79 Sitka spruce trees

Description

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.

Examples

data(spruce)
spruce$contr <- ifelse(spruce$ozone=="enriched", 0, 1)
sitka88 <- spruce[spruce$wave <= 5,]
sitka89 <- spruce[spruce$wave > 5,]
fit.88 <- geese(logsize ~ as.factor(wave) + contr +
                          I(time/100*contr) - 1,
                id=id, data=sitka88, corstr="ar1")
summary(fit.88)fit.89 <- geese(logsize ~ as.factor(wave) + contr - 1,
                id=id, data=sitka89, corstr="ar1")
summary(fit.89)

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Dataset imported from https://www.r-project.org.