1. A method, comprising: receiving candidates for classification as true positives and false positives, wherein the candidates are associated with one of a plurality of groups; determining a classification boundary for the true positives and the false positives; calculating hinge errors for the received candidates based, at least in part, on the determined classification boundary; setting a portion of the calculated hinge errors to zero, wherein the portion comprises hinge errors corresponding to candidates on a false positive side of the determined classification boundary belonging to a group of the plurality of groups also having candidates on a true positive side of the determined classification boundary; determining a shifted classification boundary based, at least in part, on the hinge errors after setting the portion of the calculated hinge errors to zero; and identifying as true positives the candidates on a true positive side of the shifted classification boundary.