Abstract: Systems and methods for determining correlation scores for product pairs are provided. Contextual user behavior indicator data relating to a plurality of user behavior indicator types is received. A correlation score is computed for a first product and a second product for each user behavior indicator type from the plurality of user behavior indicator types. A final correlation score is computed for the first product and the second product by combining the computed correlation scores for each user behavior indicator type. The computed final correlation score for the first product and the second product is stored into a first data storage.

Abstract: A system and method of determining the level of diversity for a search query are described. Distances between leaf categories in a hierarchical category tree are determined using co-click counts between the leaf categories for a query. Coordinate representations of the leaf categories are determined using the distances between the leaf categories. A diversity score for the query is determined using the coordinate representations. The diversity score represents a degree of variability in what different users find relevant to the query. In some embodiments, determining distances between leaf categories comprises determining the distances using a normalization of the co-click counts that uses co-impression counts between the leaf categories for the query. In some embodiments, a manifold learning algorithm is used to determine the coordinate representations. In some embodiments, multi-dimensional scaling is used to determine the coordinate representations.

Abstract: The stereo calibration apparatus includes an image input device inputting an image from each of two image pickup devices, a straight-line detector detecting at least four straight lines from each of two input images, a straight-line correspondence detector detecting at least four sets of corresponding lines by using an image feature in a neighboring area of the straight line, and a transformation matrix calculator calculating a transformation matrix between two image pickup devices from the sets of corresponding lines.

Abstract: The stereo calibration apparatus includes an image input device inputting an image from each of two image pickup devices, a straight-line detector detecting at least four straight lines from each of two input images, a straight-line correspondence detector detecting at least four sets of corresponding lines by using an image feature in a neighboring area of the straight line, and a transformation matrix calculator calculating a transformation matrix between two image pickup devices from the sets of corresponding lines.