ANSI C code from the article "Smoothing and Interpolation with Finite Differences" by Paul H. C. Eilers, paul@dcmr.nl in "Graphics Gems IV", Academic Press, 1994 files: smooth1.c: Smoothing and interpolation with first differences. smooth2.c: Smoothing and interpolation with second differences. smooth3.c: Smoothing and interpolation with any difference equation.