Damage scores (ordinal scale) for Picea Sitchesis shoots at two dates, at four temperatures, and 4 ozone Levels
An artificial data frame with 18 observations in each of three groups.
temperature in degrees Celcius
Ozone concentration at 4 different levels
the damage score from 0-4, higher is more damage
The number of occurrences of this group
P.W. Lucas, D.A. Cottam, L.J. Sheppard, B.J. Francis (1988). "Growth Responses and Delayed Winter Hardening in Sitka Spruce Following Summer Exposure to Ozone," New Phytologist, Vol. 108, pp. 495-504.
data(picea)