ABSTRACT
Exploratory data analysis consists of a collection of tools, and the question of which tool to employ depends on the data and on the objective of the study. After an initial exploratory phase, the exploratory and confirmatory processes to some extent co-occur, with results of the confirmatory phase often motivating further exploration. Fertilization guidelines for nitrogen and potassium in California are based on the level of nitrate-nitrogen and potassium measured in the stem. The preliminary analyses indicate that the gross trend of declining yield in the north end of the field is probably caused by aeration stress associated with moisture retention by the heavy clay soil. The southern part of the field has higher yield overall, with the southwest corner having the highest yield. The yield trend generally appears fairly smooth except for two anomalously low areas: a triangular-shaped region on the western edge and the entire eastern edge.
