Timur A. Fatkhullin
5279d1c41a
start developing of FITPACK C++ bindings mount_server.cpp: fix compilation error with GCC15
140 lines
4.2 KiB
Fortran
140 lines
4.2 KiB
Fortran
recursive subroutine splev(t,n,c,nc,k,x,y,m,e,ier)
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c subroutine splev evaluates in a number of points x(i),i=1,2,...,m
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c a spline s(x) of degree k, given in its b-spline representation.
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c
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c calling sequence:
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c call splev(t,n,c,nc,k,x,y,m,e,ier)
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c
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c input parameters:
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c t : array,length n, which contains the position of the knots.
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c n : integer, giving the total number of knots of s(x).
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c c : array,length nc, containing the b-spline coefficients.
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c the length of the array, nc >= n - k -1.
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c further coefficients are ignored.
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c k : integer, giving the degree of s(x).
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c x : array,length m, which contains the points where s(x) must
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c be evaluated.
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c m : integer, giving the number of points where s(x) must be
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c evaluated.
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c e : integer, if 0 the spline is extrapolated from the end
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c spans for points not in the support, if 1 the spline
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c evaluates to zero for those points, if 2 ier is set to
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c 1 and the subroutine returns, and if 3 the spline evaluates
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c to the value of the nearest boundary point.
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c
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c output parameter:
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c y : array,length m, giving the value of s(x) at the different
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c points.
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c ier : error flag
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c ier = 0 : normal return
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c ier = 1 : argument out of bounds and e == 2
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c ier =10 : invalid input data (see restrictions)
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c
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c restrictions:
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c m >= 1
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c-- t(k+1) <= x(i) <= x(i+1) <= t(n-k) , i=1,2,...,m-1.
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c
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c other subroutines required: fpbspl.
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c
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c references :
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c de boor c : on calculating with b-splines, j. approximation theory
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c 6 (1972) 50-62.
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c cox m.g. : the numerical evaluation of b-splines, j. inst. maths
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c applics 10 (1972) 134-149.
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c dierckx p. : curve and surface fitting with splines, monographs on
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c numerical analysis, oxford university press, 1993.
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c
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c author :
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c p.dierckx
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c dept. computer science, k.u.leuven
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c celestijnenlaan 200a, b-3001 heverlee, belgium.
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c e-mail : Paul.Dierckx@cs.kuleuven.ac.be
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c
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c latest update : march 1987
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c
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c++ pearu: 11 aug 2003
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c++ - disabled cliping x values to interval [min(t),max(t)]
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c++ - removed the restriction of the orderness of x values
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c++ - fixed initialization of sp to double precision value
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c
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c ..scalar arguments..
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integer n, k, m, e, ier
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c ..array arguments..
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real*8 t(n), c(nc), x(m), y(m)
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c ..local scalars..
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integer i, j, k1, l, ll, l1, nk1
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c++..
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integer k2
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c..++
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real*8 arg, sp, tb, te
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c ..local array..
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real*8 h(20)
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c ..
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c before starting computations a data check is made. if the input data
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c are invalid control is immediately repassed to the calling program.
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ier = 10
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c-- if(m-1) 100,30,10
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c++..
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if (m .lt. 1) go to 100
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c..++
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c-- 10 do 20 i=2,m
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c-- if(x(i).lt.x(i-1)) go to 100
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c-- 20 continue
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ier = 0
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c fetch tb and te, the boundaries of the approximation interval.
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k1 = k + 1
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c++..
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k2 = k1 + 1
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c..++
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nk1 = n - k1
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tb = t(k1)
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te = t(nk1 + 1)
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l = k1
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l1 = l + 1
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c main loop for the different points.
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do 80 i = 1, m
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c fetch a new x-value arg.
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arg = x(i)
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c check if arg is in the support
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if (arg .lt. tb .or. arg .gt. te) then
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if (e .eq. 0) then
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goto 35
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else if (e .eq. 1) then
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y(i) = 0
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goto 80
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else if (e .eq. 2) then
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ier = 1
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goto 100
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else if (e .eq. 3) then
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if (arg .lt. tb) then
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arg = tb
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else
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arg = te
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endif
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endif
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endif
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c search for knot interval t(l) <= arg < t(l+1)
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c++..
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35 if (arg .ge. t(l) .or. l1 .eq. k2) go to 40
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l1 = l
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l = l - 1
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go to 35
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c..++
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40 if(arg .lt. t(l1) .or. l .eq. nk1) go to 50
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l = l1
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l1 = l + 1
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go to 40
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c evaluate the non-zero b-splines at arg.
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50 call fpbspl(t, n, k, arg, l, h)
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c find the value of s(x) at x=arg.
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sp = 0.0d0
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ll = l - k1
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do 60 j = 1, k1
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ll = ll + 1
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sp = sp + c(ll)*h(j)
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60 continue
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y(i) = sp
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80 continue
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100 return
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end
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