During the preprocessing stage, the database was transformed in order to
include a distinct wine sample (with all tests) per row. To avoid discarding
examples, only the most common physicochemical tests were selected. Table 1
presents the physicochemical statistics per dataset. Regarding the preferences,
each sample was evaluated by a minimum of three sensory assessors (using blind
tastes), which graded the wine in a scale that ranges from 0 (very bad) to 10
(excellent). The final sensory score is given by the median of these evaluations.
Fig. 1 plots the histograms of the target variable, denoting a typical normal
shape distribution (i.e. with more normal grades that extreme ones).