##
Growth Curves for Sitka Spruce Trees in 1988

### Description

The `Sitka`

data frame has 395 rows and 4 columns. It gives repeated
measurements on the log-size of 79 Sitka spruce trees, 54 of which
were grown in ozone-enriched chambers and 25 were controls. The size
was measured five times in 1988, at roughly monthly intervals.

### Usage

```
Sitka
```

### Format

This data frame contains the following columns:

`size`

measured size (height times diameter squared) of
tree, on log scale.

`Time`

time of measurement in days since 1 January 1988.

`tree`

number of tree.

`treat`

either `"ozone"`

for an ozone-enriched
chamber or `"control"`

.

### Source

P. J. Diggle, K.-Y. Liang and S. L. Zeger (1994)
*Analysis of Longitudinal Data.*
Clarendon Press, Oxford

### References

Venables, W. N. and Ripley, B. D. (2002)
*Modern Applied Statistics with S.* Fourth edition. Springer.

### See Also

`Sitka89`

.