X-Git-Url: http://git.kpe.io/?a=blobdiff_plain;ds=sidebyside;f=libctsupport%2Fcubicinterp.cpp;h=fa51f7b47fd52f15ee6a5dcf6c48925922c943cf;hb=2efdad35a3d335dfa84a8576f41588dbd7dd8958;hp=d95f9056b15963ff80d389a7db91bfe5ab1b8dc0;hpb=2e09cc8b6f6ac842d06b45cae6a9205a33eece53;p=ctsim.git

diff --git a/libctsupport/cubicinterp.cpp b/libctsupport/cubicinterp.cpp
index d95f905..fa51f7b 100644
--- a/libctsupport/cubicinterp.cpp
+++ b/libctsupport/cubicinterp.cpp
@@ -2,7 +2,7 @@
 **  This is part of the CTSim program
 **  Copyright (c) 1983-2001 Kevin Rosenberg
 **
-**  $Id: cubicinterp.cpp,v 1.2 2001/02/09 01:55:24 kevin Exp $
+**  $Id: cubicinterp.cpp,v 1.3 2001/02/09 14:34:16 kevin Exp $
 **
 **  This program is free software; you can redistribute it and/or modify
 **  it under the terms of the GNU General Public License (version 2) as
@@ -26,6 +26,11 @@
 CubicInterpolator::CubicInterpolator (const double* const y, const int n)
   : m_pdY(y), m_n(n)
 {
+  // Precalculate 2nd derivative of y and put in m_pdY2
+  // Calculated by solving set of simultaneous cubic spline equations
+  // Only n-2 cubic spline equations, but able to make two more
+  // equations by setting second derivative to 0 at ends 
+
   m_pdY2 = new double [n];
   m_pdY2[0] = 0;   // second deriviative = 0 at beginning and end
   m_pdY2[n-1] = 0;