Timur A. Fatkhullin
5279d1c41a
start developing of FITPACK C++ bindings mount_server.cpp: fix compilation error with GCC15
76 lines
2.4 KiB
Fortran
76 lines
2.4 KiB
Fortran
recursive subroutine spalde(t,n,c,nc,k1,x,d,ier)
|
|
implicit none
|
|
c subroutine spalde evaluates at a point x all the derivatives
|
|
c (j-1)
|
|
c d(j) = s (x) , j=1,2,...,k1
|
|
c of a spline s(x) of order k1 (degree k=k1-1), given in its b-spline
|
|
c representation.
|
|
c
|
|
c calling sequence:
|
|
c call spalde(t,n,c,k1,x,d,ier)
|
|
c
|
|
c input parameters:
|
|
c t : array,length n, which contains the position of the knots.
|
|
c n : integer, giving the total number of knots of s(x).
|
|
c c : array,length nc, which contains the b-spline coefficients.
|
|
c nc : integer, giving the total number of coefficients (must be >= n-k1)
|
|
c k1 : integer, giving the order of s(x) (order=degree+1)
|
|
c x : real, which contains the point where the derivatives must
|
|
c be evaluated.
|
|
c
|
|
c output parameters:
|
|
c d : array,length k1, containing the derivative values of s(x).
|
|
c ier : error flag
|
|
c ier = 0 : normal return
|
|
c ier =10 : invalid input data (see restrictions)
|
|
c
|
|
c restrictions:
|
|
c t(k1) <= x <= t(n-k1+1)
|
|
c
|
|
c further comments:
|
|
c if x coincides with a knot, right derivatives are computed
|
|
c ( left derivatives if x = t(n-k1+1) ).
|
|
c
|
|
c other subroutines required: fpader.
|
|
c
|
|
c references :
|
|
c de boor c : on calculating with b-splines, j. approximation theory
|
|
c 6 (1972) 50-62.
|
|
c cox m.g. : the numerical evaluation of b-splines, j. inst. maths
|
|
c applics 10 (1972) 134-149.
|
|
c dierckx p. : curve and surface fitting with splines, monographs on
|
|
c numerical analysis, oxford university press, 1993.
|
|
c
|
|
c author :
|
|
c p.dierckx
|
|
c dept. computer science, k.u.leuven
|
|
c celestijnenlaan 200a, b-3001 heverlee, belgium.
|
|
c e-mail : Paul.Dierckx@cs.kuleuven.ac.be
|
|
c
|
|
c latest update : march 1987
|
|
c
|
|
c ..scalar arguments..
|
|
integer n,nc,k1,ier
|
|
real*8 x
|
|
c ..array arguments..
|
|
real*8 t(n),c(nc),d(k1)
|
|
c ..local scalars..
|
|
integer l,nk1
|
|
c ..
|
|
c before starting computations a data check is made. if the input data
|
|
c are invalid control is immediately repassed to the calling program.
|
|
ier = 10
|
|
nk1 = n-k1
|
|
if(x.lt.t(k1) .or. x.gt.t(nk1+1)) go to 300
|
|
c search for knot interval t(l) <= x < t(l+1)
|
|
l = k1
|
|
100 if(x.lt.t(l+1) .or. l.eq.nk1) go to 200
|
|
l = l+1
|
|
go to 100
|
|
200 if(t(l).ge.t(l+1)) go to 300
|
|
ier = 0
|
|
c calculate the derivatives.
|
|
call fpader(t,n,c,k1,x,l,d)
|
|
300 return
|
|
end
|