This article introduces a method for computing weighted averages on spheres based on least squares minimization that respects spherical distance. We prove existence and uniqueness properties of the weighted averages, and give fast iterative algorithms with linear and quadratic convergence rates. Our methods are appropriate to problems involving averages of spherical data in meteorological, geophysical, and astronomical applications. One simple application is a method for smooth averaging of quaternions, which generalizes Shoemake's spherical linear interpolation.The weighted averages methods allow a novel method of defining Bézier and spline curves on spheres, which provides direct generalization of Bézier and B-spline curves to spherical spline curves. We present a fast algorithm for spline interpolation on spheres. Our spherical splines allow the use of arbitrary knot positions; potential applications of spherical splines include smooth quaternion curves for applications in graphics, animation, robotics, and motion planning.

This paper discusses determination of the ranks, in lexicographic lists, of the symmetries and proper symmetries of the n-cube and of its colorations by r colors, up to these symmetries.

A basic algorithm for solving many discrete problems is the so-called “backtracking” algorithm. The basic problem is that of generating the elements of a subset $S_0 $ of a finite set in an efficient manner. If a group G acts on $S_0 $, then one might wish to obtain only nonisomorphic elements of $S_0 $. In this paper the basic backtracking algorithm is described in terms of chains of partitions on the set S. The corresponding isomorph rejection problem is described in terms of G-invariant chains of partitions on S. Examples and flow charts are given.