# L2CXCV: A Fortran 77 package for least squares convex/concave data smoothing

## Description

Abstract Fortran 77 software is given for least squares smoothing to data values contaminated by random errors subject to one sign change in the second divided differences of the smoothed values, where the location of the sign change is also unknown of the optimization problem. A highly useful description of the constraints is that they follow from the assumption of initially increasing and subsequently decreasing rates of change, or vice versa, of the process considered. The underlying algorithm part... Title of program: L2CXCV Catalogue Id: ADXM_v1_0 Nature of problem <ul type="disc"> <li> Analysis of processes that show initially increasing and then decreasing rates of change (sigmoid shape), as for example in heat curves, reactor stability conditions, evolution curves, photoemission yields, growth models, utility functions etc. <li> Identifying an unknown convex / concave (sigmoid) function from some measurements of its values that contain random errors. Also, identifying the inflection point of this sigmoid function.</ul> Versions of this program held in the CPC repository in Mendeley Data ADXM_v1_0; L2CXCV; 10.1016/j.cpc.2005.12.004 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019)