Each row of the data set is a set of 90 measurements at a river in some place in Europe.
There are 11 predictors. The response is the logarithm of the abundance of a certain
class of algae. Description: The columns are:
1. season, categorical (1,2,3,4 for winter, spring, summer and autumn)
2. river size (categorical) (1,2,3 for small, medium and large)
3. fluid velocity (categorical) (1,2,3 for low, medium and high)
4-11 (numerci): content of nitrogen in the form of nitrates, nitrites and ammonia, and other
chemical compounds.
Col. 12 ia the response: abundance of a type of algae (type 6 in the complete file). For
simplicity we deleted the rows with missing values and took the logarithm of the response.