Quadratic spline subroutine package

Water-Resources Investigations Report 82-41



A continuous piecewise quadratic function with continuous first derivative is devised for approximating a single-valued, but unknown, function represented by a set of discrete points. The quadratic is proposed as a treatment intermediate between using the angular (but reliable, easily constructed and manipulated) piecewise linear function and using the smoother (but occasionally erratic) cubic spline. Neither iteration nor the solution of a system of simultaneous equations is necessary to determining the coefficients. Several properties of the quadratic function are given. A set of five short FORTRAN subroutines is provided for generating the coefficients (QSC), finding function value and derivatives (QSY), integrating (QSI), finding extrema (QSE), and computing arc length and the curvature-squared integral (QSK). (USGS)

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Quadratic spline subroutine package
Series title Water-Resources Investigations Report
Series number 82-41
DOI 10.3133/wri8241
Year Published 1982
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 16 p.