1. A computing apparatus comprising: a memory configured to store N first vectors in a d-dimensional binary vector space consisting of binary values(0 or 1), wherein each of the N first vectors is represented by d binary elements, wherein N is an integer equal to or larger than 2, and d is an integer equal to or larger than 1; and a processor configured to: acquire a second vector in the d-dimensional binary vector space, the second vector represented by d binary elements; extract M first vectors out of the N first vectors, M being an integer, larger than zero, and smaller than N, wherein respective distances between the M first vectors and the second vector satisfy a predetermined condition; calculate a distribution of the distances between the M first vectors and the second vector; acquire respective first kernel functions for the distances in a distance range, the distance range being at least a part of a possible distance range between the N first vectors and the second vector; generate a second kernel function based on the distribution and the first kernel functions; and calculate an occurrence probability of the second vector with respect to the N first vectors based on the second kernel function.