bsppp.f
SUBROUTINE BSPPP (T, A, N, K, LDC, C, XI, LXI, WORK)
C***BEGIN PROLOGUE BSPPP
C***PURPOSE Convert the B-representation of a B-spline to the piecewise
C polynomial (PP) form.
C***LIBRARY SLATEC
C***CATEGORY E3, K6
C***TYPE SINGLE PRECISION (BSPPP-S, DBSPPP-D)
C***KEYWORDS B-SPLINE, PIECEWISE POLYNOMIAL
C***AUTHOR Amos, D. E., (SNLA)
C***DESCRIPTION
C
C Written by Carl de Boor and modified by D. E. Amos
C
C Abstract
C BSPPP is the BSPLPP routine of the reference.
C
C BSPPP converts the B-representation (T,A,N,K) to the
C piecewise polynomial (PP) form (C,XI,LXI,K) for use with
C PPVAL. Here XI(*), the break point array of length LXI, is
C the knot array T(*) with multiplicities removed. The columns
C of the matrix C(I,J) contain the right Taylor derivatives
C for the polynomial expansion about XI(J) for the intervals
C XI(J) .LE. X .LE. XI(J+1), I=1,K, J=1,LXI. Function PPVAL
C makes this evaluation at a specified point X in
C XI(1) .LE. X .LE. XI(LXI(1) .LE. X .LE. XI+1)
C
C Description of Arguments
C Input
C T - knot vector of length N+K
C A - B-spline coefficient vector of length N
C N - number of B-spline coefficients
C N = sum of knot multiplicities-K
C K - order of the B-spline, K .GE. 1
C LDC - leading dimension of C, LDC .GE. K
C
C Output
C C - matrix of dimension at least (K,LXI) containing
C right derivatives at break points
C XI - XI break point vector of length LXI+1
C LXI - number of break points, LXI .LE. N-K+1
C WORK - work vector of length K*(N+3)
C
C Error Conditions
C Improper input is a fatal error
C
C***REFERENCES Carl de Boor, Package for calculating with B-splines,
C SIAM Journal on Numerical Analysis 14, 3 (June 1977),
C pp. 441-472.
C***ROUTINES CALLED BSPDR, BSPEV, XERMSG
C***REVISION HISTORY (YYMMDD)
C 800901 DATE WRITTEN
C 890831 Modified array declarations. (WRB)
C 890831 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
C 900326 Removed duplicate information from DESCRIPTION section.
C (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE BSPPP