Visual interpolation of data

Following a precise definition of shape-preserving interpolating Functions to data. we construct ill a new and elementary manner such a cubic spline S -2 is an element of C-2, letting two additional knots per interval. We give an explicit description of S-2 which has satisfactory properties in all th e aspects. All the results in the paper-obtained with elementary calculus-a re based oil the behavior of the derivative of ally smooth interpolating fu nction to these data. (C) 2001 Elsevier Science Ltd. All rights reserved.