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subroutine profil(iopt,tx,nx,ty,ny,c,kx,ky,u,nu,cu,ier)
c if iopt=0 subroutine profil calculates the b-spline coefficients of
c the univariate spline f(y) = s(u,y) with s(x,y) a bivariate spline of
c degrees kx and ky, given in the b-spline representation.
c if iopt = 1 it calculates the b-spline coefficients of the univariate
c spline g(x) = s(x,u)
c
c calling sequence:
c call profil(iopt,tx,nx,ty,ny,c,kx,ky,u,nu,cu,ier)
c
c input parameters:
c iopt : integer flag, specifying whether the profile f(y) (iopt=0)
c or the profile g(x) (iopt=1) must be determined.
c tx : real array, length nx, which contains the position of the
c knots in the x-direction.
c nx : integer, giving the total number of knots in the x-direction
c ty : real array, length ny, which contains the position of the
c knots in the y-direction.
c ny : integer, giving the total number of knots in the y-direction
c c : real array, length (nx-kx-1)*(ny-ky-1), which contains the
c b-spline coefficients.
c kx,ky : integer values, giving the degrees of the spline.
c u : real value, specifying the requested profile.
c tx(kx+1)<=u<=tx(nx-kx), if iopt=0.
c ty(ky+1)<=u<=ty(ny-ky), if iopt=1.
c nu : on entry nu must specify the dimension of the array cu.
c nu >= ny if iopt=0, nu >= nx if iopt=1.
c
c output parameters:
c cu : real array of dimension (nu).
c on succesful exit this array contains the b-spline
c ier : integer error flag
c ier=0 : normal return
c ier=10: invalid input data (see restrictions)
c
c restrictions:
c if iopt=0 : tx(kx+1) <= u <= tx(nx-kx), nu >=ny.
c if iopt=1 : ty(ky+1) <= u <= ty(ny-ky), nu >=nx.
c
c other subroutines required:
c fpbspl
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 iopt,nx,ny,kx,ky,nu,ier
real*8 u
c ..array arguments..
real*8 tx(nx),ty(ny),c((nx-kx-1)*(ny-ky-1)),cu(nu)
c ..local scalars..
integer i,j,kx1,ky1,l,l1,m,m0,nkx1,nky1
real*8 sum
c ..local array
real*8 h(6)
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.
kx1 = kx+1
ky1 = ky+1
nkx1 = nx-kx1
nky1 = ny-ky1
ier = 10
if(iopt.ne.0) go to 200
if(nu.lt.ny) go to 300
if(u.lt.tx(kx1) .or. u.gt.tx(nkx1+1)) go to 300
c the b-splinecoefficients of f(y) = s(u,y).
ier = 0
l = kx1
l1 = l+1
110 if(u.lt.tx(l1) .or. l.eq.nkx1) go to 120
l = l1
l1 = l+1
go to 110
120 call fpbspl(tx,nx,kx,u,l,h)
m0 = (l-kx1)*nky1+1
do 140 i=1,nky1
m = m0
sum = 0.
do 130 j=1,kx1
sum = sum+h(j)*c(m)
m = m+nky1
130 continue
cu(i) = sum
m0 = m0+1
140 continue
go to 300
200 if(nu.lt.nx) go to 300
if(u.lt.ty(ky1) .or. u.gt.ty(nky1+1)) go to 300
c the b-splinecoefficients of g(x) = s(x,u).
ier = 0
l = ky1
l1 = l+1
210 if(u.lt.ty(l1) .or. l.eq.nky1) go to 220
l = l1
l1 = l+1
go to 210
220 call fpbspl(ty,ny,ky,u,l,h)
m0 = l-ky
do 240 i=1,nkx1
m = m0
sum = 0.
do 230 j=1,ky1
sum = sum+h(j)*c(m)
m = m+1
230 continue
cu(i) = sum
m0 = m0+nky1
240 continue
300 return
end
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