A $O(n)$ algorithm for projecting a vector on the intersection of a hyperplane and $R^n_+$

We present a O (η) time algorithm for the projection of a vector on the intersection of a hyperplane and R n + . A linear-time median-finding algorithm is used to determine the median of the components of the vector to be projected. This extends a previous result of Maculan and Paula Jr. concerning the projection on the η-dimensional simplex.