Table 1 Rating matrix data set with four users (rows) and three items (columns), with the rating of each user given in an ordinal scale of three points
U1Embedded Image 2Embedded Image ?Embedded Image 3
U2Embedded Image 5Embedded Image 2Embedded Image ?
U3Embedded Image 3Embedded Image 3Embedded Image 1
U4Embedded Image ?Embedded Image 2Embedded Image 2
  • ? denotes missing values that need to be predicted.