# Semi-code for curfit.h

# define the permitted types of curves

define	CHEBYSHEV	1
define	LEGENDRE	2
define	L2SPLINE4	3

# define the weighting flags

define	NORMAL		1	# user enters weights
define	UNIFORM		2	# equal weights, weight 1.0
define	SPACING		3	# weigth proportional to spacing of data points

define	SPLINE_ORDER	4

# set up the curve fitting structure

define	LEN_CVSTRUCT

struct curfit {

define	CV_TYPE		Memi[]		# Type of curve to be fitted
define	CV_ORDER	Memi[]		# Order of the fit
define	CV_NPIECES	Memi[]		# Number of polynomial pieces, spline
define	CV_NCOEFF	Memi[]		# Number of coefficients
define	CV_XMAX		Memr[]		# Maximum x value
define	CV_XMIN		Memr[]		# Minimum x value
define	CV_RANGE	Memr[]		# Xmax minus xmin
define	CV_MAXMIN	Memr[]		# Xmax plus xmin
define	CV_SPACING	Memr[]		# Knot spacing for splines
define	CV_YNORM	Memr[]		# Norm of the Y vector
define	CV_NPTS		Memi[]		# Number of data points

define	CV_MATRIX	Memi[]		# Pointer to original matrix
define	CV_CHOFAC	Memi[]		# Pointer to Cholesky factorization
define	CV_BASIS	Memi[]		# Pointer to basis functions
define	CV_VECTOR	Memi[]		# Pointer to  vector
define	CV_COEFF	Memi[]		# Pointer to coefficient vector
define	CV_LEFT		Memi[]		#

}

# matrix and vector element definitions

define	MATRIX		Memr[$1+($2-1)*NCOEFF(cv)]	# Matrix element
define	CHOFAC		Memr[$1+($2-1)*NCOEFF(cv)]	# Triangular matrix
define	VECTOR		Memr[$1+$2]			# Right side
define	COEFF		Memr[$1+$2]			# Coefficient vector
define	LEFT		Memi[$1+$2]

# matrix and vector definitions

define	MAT		Memr[$1]
define	CHO		Memr[$1]
define	VECT		Memr[$1]
define	COF		Memr[$1]

# semi-code for the initialization procedure

include "curfit.h"

# CVINIT --  Procedure to set up the curve  descriptor.

procedure cvinit (cv, curve_type, order, xmin, xmax)

pointer	cv		# pointer to curve descriptor structure
int	curve_type	# type of curve to be fitted
int	order		# order of curve to be fitted, or in the case of the
			# spline the number of polynomial pieces to be fit
real	xmin		# minimum value of x
real	xmax		# maximum value of x

begin
	# allocate space for the curve descriptor
	call smark (sp)
	call salloc (cv, LEN_CVSTRUCT, TY_STRUCT)

	if (order < 1)
	    call error (0, "CVINIT: Illegal order.")

	if (xmax <= xmin)
	    call error (0, "CVINIT: xmax <= xmin.")

	switch (curve_type) {
	case CHEBYSHEV, LEGENDRE:
	    CV_ORDER(cv) = order
	    CV_NCOEFF(CV) = order
	    CV_RANGE(cv) = xmax - xmin
	    CV_MAXMIN(cv) = xmax + xmin
	case L2SPLINE4:
	    CV_ORDER(cv) = SPLINE_ORDER
	    CV_NCOEFF(cv) = order + SPLINE_ORDER - 1
	    CV_NPIECES(cv) = order
	    CV_SPACING(cv) = (xmax - xmin) / order
	default:
	    call error (0, "CVINIT: Unknown curve type.")
	}

	CV_TYPE(cv) = curve_type
	CV_XMIN(cv) = xmin
	CV_XMAX(cv) = xmax

	# allocate space for the matrix and vectors
	call calloc (CV_MATRIX(cv), CV_ORDER(cv)*CV_NCOEFF(cv), TY_REAL)
	call calloc (CV_CHOFAC(cv), CV_ORDER(cv)*CV_NCOEFF(cv), TY_REAL)
	call calloc (CV_VECTOR(cv), CV_NCOEFF(cv), TY_REAL)
	call calloc (CV_COEFF(cv), CV_NCOEFF(cv), TY_REAL)

	# initialize pointer to basis functions to null
	CV_BASIS(cv) = NULL

	CV_NPTS(cv) = 0
	CV_YNORM(cv) = 0.
end

# semi-code for cvaccum

include "curfit.h"

# CVACCUM -- Procedure to add a single point to the data set.

procedure cvaccum (cv, x, y, w, wtflag)

pointer	cv		# curve descriptor
real	x		# x value
real	y		# y value
real	w		# weight of the data point
int	wtflag		# type of weighting desired

begin
	# calculate the weights
	switch (wtflag) {
	case UNIFORM:
	    w = 1.0
	case NORMAL, SPACING: 		# problem spacing
	default:
	    w = 1.0
	}

	# caculate all non-zero basis functions for a given data point
	switch (CV_TYPE(cv)) {
	case CHEBYSHEV:
	    left = 1
	    call chebyshev (cv, x, basis)
	case LEGENDRE:
	    left = 1
	    call legendre (cv, x, basis)
	case L2SPLINE4:
	    call l2spline4 (cv, x, left, basis)
	}

	# accumulate into the matrix
	leftm1 = left - 1
	vptr = CV_VECTOR(cv) - 1
	do i = 1, CV_ORDER(cv) {
	    bw = basis[i] * w
	    jj = leftm1 + i
	    mptr = CV_MATRIX(cv) + jj - 1
	    VECTOR(vptr, jj) = VECTOR(vptr, jj) + bw * y
	    ii = 1
	    do j = i, CV_ORDER(cv) {
		MATRIX(mptr, ii) = MATRIX(mptr, ii) + basis[j] * bw
		ii = ii + 1
	    }
	}

	CV_NPTS(cv) = CV_NPTS(cv) + 1
	CV_YNORM(cv) = CV_YNORM(cv) + w * y * y
end

# semi-code for cvreject

include "curfit.h"

# CVREJECT -- Procedure to subtract a single datapoint from the data set
# to be fitted.

procedure cvreject (cv, x, y, w)

pointer	cv		# curve fitting image descriptor
real	x		# x value
real	y		# y value
real	w		# weight of the data point

begin
	# caculate all type non-zero basis functions for a given data point
	switch (CV_TYPE(cv)) {
	case CHEBYSHEV:
	    left = 1
	    call chebyshev (cv, x, basis)
	case LEGENDRE:
	    left = 1
	    call legendre (cv, x, basis)
	case L2SPLINE4:
	    call l2spline4 (cv, x, left, basis)
	}

	# subtract the data point from the matrix
	leftm1 = left - 1
	vptr = CV_VECTOR(cv) - 1
	do i = 1, CV_ORDER(cv) {
	    bw = basis[i] * w
	    jj = leftm1 + i
	    mptr = CV_MATRIX(cv) + jj - 1
	    VECTOR(vptr, jj) = VECTOR(vptr, jj) - bw * y
	    ii = 1
	    do j = i, CV_ORDER(cv) {
		MATRIX(mptr, ii) = MATRIX(mptr, ii) - basis[j] * bw
		ii = ii + 1
	    }
	}

	CV_NPTS(cv) = CV_NPTS(cv) - 1
	CV_NORM(cv) = CV_NORM(cv) - w * y * y
end

# semi-code for cvsolve

include "curfit.h"

# CVSOLVE -- Procedure to  solve a matrix equation of the form Ax = B.
# The Cholesky factorization of matrix A is calculated in the first
# step, followed by forward and back substitution to solve for the vector
# x.

procedure cvsolve (cv, ier)

pointer	cv 		# pointer to the image descriptor structure
int	ier		# ier = 0, everything OK
			# ier = 1, matrix is singular

begin
	# solve matrix by adapting Deboor's bchfac.f and bchslv.f routines
	# so that the original matrix and vector are not destroyed

	call chofac (MAT(CV_MATRIX(cv)), CV_ORDER(cv), CV_NCOEFF(cv),
		     CHO(CV_CHOFAC(cv)), ier)
	call choslv (CHO(CV_CHOFAC(cv)), CV_ORDER(cv), CV_NCOEFF(cv),
		     VECT(CV_VECTOR(cv)), COF(CV_COEFF(cv)))
end

# semi-code for cvfit

include "curfit.h"

# CVFIT -- Procedure to fit a curve to an array of data points x and y with
# weights w.

procedure cvfit (x, y, w, npts, wtflag, ier)

real	x[npts]		# array of abcissa
real	y[npts]		# array of ordinates
real	w[npts]		# array of weights
int	wtflag		# type of weighting
int	ier

begin
	# calculate weights
	switch (wtflag) {
	case UNIFORM:
	    call amovkr (1., w, npts)
	case SPACING:
	    w[1] = x[2] - x[1]			# check for npts > 1
	    do i = 2, npts - 1
		w[i] = x[i+1] - x[i-1]
	    w[npts] = x[npts] - x[npts-1]
	case NORMAL:
	default:
	    call amovkr (1., w, npts)
	}

	# accumulate data points
	do i = 1, npts {

	    CV_NPTS(cv) = CV_NPTS(cv) + 1

	    # calculate the norm of the Y vector
	    CV_YNORM(cv) = CV_YNORM(cv) + w[i] * y[i] * y[i]

	    # calculate non zero basis functions
	    switch (CV_TYPE(cv)) {
	    case CHEBYSHEV:
		left = 1
		call chebyshev (cv, x, basis)
	    case LEGENDRE:
		left = 1
		call legendre (cv, x, basis)
	    case L2SPLINE4:
		call l2spline4 (cv, x, left, basis)
	    }

	    # accumulate the matrix
	    leftm1 = left - 1
	    vptr = CV_VECTOR(cv) - 1
	    do i = 1, CV_ORDER(cv) {
	        bw = basis[i] * w
	        jj = leftm1 + i
		mptr = CV_MATRIX(cv) + jj - 1
	        VECTOR(vptr, jj) = VECTOR(vptr, jj) + bw * y
	        ii = 1
	        do j = i, CV_ORDER(cv) {
		    MATRIX(mptr, ii) = MATRIX(mptr, ii) + basis[j] * bw
		    ii = ii + 1
	        }
	    }
	}

	# solve the matrix
	ier = 0
	call chofac (MAT(CV_MATRIX(cv)), CV_ORDER(cv), CV_NCOEFF(cv),
		     CHO(CV_CHOFAC(cv)), ier)
	call choslv (CHO(CV_CHOFAC(cv)), CV_ORDER(cv), CV_NCOEFF(cv),
		     VECT(CV_VECTOR(cv)), COF(CV_COEFF(cv)))
end

# semi-code for cvrefit

include "curfit.com"

# CV_REFIT -- Procedure to refit the data assuming that the x and w values do
# not change.

procedure cvrefit (cv, x, y, w, ier)

pointer	cv
real	x[ARB]
real	y[ARB]
real	w[ARB]
int	ier

begin
	# if first call to refit then calculate and store the basis
	# functions

	vcptr = CV_VECTOR(cv) - 1
	do i = 1, NCOEFF(cv)
	    VECTOR(vcptr+i) = 0.

	CV_YNORM(cv) = 0.
	lptr = CV_LEFT(cv) - 1
	bcptr = CV_BASIS(cv) - CV_NPTS(cv)

	if (CV_BASIS(cv) == NULL) {

	    call calloc (CV_BASIS(cv), CV_NPTS(cv)*CV_ORDER(cv), TY_REAL)
	    call calloc (CV_LEFT(cv), CV_NPTS(cv), TY_INT)

	    do l = 1, CV_NPTS(cv) {
		bptr = bcptr + l * CV_NPTS(cv)
		switch (CV_TYPE(cv)) {
		case LEGENDRE:
		    LEFT(lptr+l) = 1
		    call legendre (cv, x, BASIS(bptr))
		case CHEBYSHEV:
		    LEFT(lptr+l) = 1
		    call chebyshev (cv, x, BASIS(bptr))
		case L2SPLINE4:
		    call l2spline4 (cv, x, LEFT(lptr+l), BASIS(bptr))
		}
	    }
	}

	# reset vector to zero

	# accumulate right side of the matrix equation
	do l = 1, CV_NPTS(cv) {

	    CV_YNORM(cv) = CV_YNORM(cv) + w[l] * y[l] * y[l]
	    leftm1 = LEFT(lptr+l) - 1
	    bptr = bcptr + l * CV_NPTS(cv) 

	    do i = 1, CV_ORDER(cv) {
		vptr = vcptr + leftm1 + i
		VECTOR(vptr) = VECTOR(vptr) + BASIS(bptr) * w[l] * y[l]
	    }
	}

	# solve the matrix
	call choslv (CHOFAC(CV_CHOFAC(cv)), CV_ORDER(cv), CV_NCOEFF(CV),
		    VECTOR(CV_VECTOR(cv)), COEFF(CV_COEFF(cv)))
end

# semi-code for cvcoeff

# CVCOEFF -- Procedure to fetch the number and magnitude of the coefficients.

procedure cvcoeff (cv, coeff, ncoeff)

pointer	cv		# pointer to the curve fitting descriptor
real	coeff[ncoeff]	# the coefficients of the fit
int	ncoeff		# the number of coefficients

begin
	ncoeff = CV_NCOEFF(cv)
	cptr = CV_COEFF(cv) - 1
	do i = 1, ncoeff
	    coeff[i] = COEFF(cptr, i)
end

# semi-code for cvvector

include "curfit.h"

# CVVECTOR -- Procedure to evaluate the fitted curve

procedure cvvector (cv, x, npts, yfit)

pointer	cv		# pointer to the curve descriptor structure
real	x[npts]		# data x values
int	npts		# number of data points
real	yfit[npts]	# the fitted y values

begin
	do l = 1, npts {

	    # calculate the non-zero basis functions
	    switch (CV_TYPE(cv) {
	    case LEGENDRE:
		left = 1
		call legendre (cv, x[l], XBASIS(CV_XBASIS(cv)))
	    case CHEBYSHEV:
		left = 1
		call chebyshev (cv, x[l], XBASIS(CV_XBASIS(cv)))
	    case L2SPLINE4:
		call l2spline4 (cv, x[l], left, XBASIS(CV_XBASIS(cv)))
	    }

	    sum = 0.0
	    leftm1 = left - 1
	    cptr = CV_COEFF(cv) - 1
	    xptr = CV_XBASIS(cv) - 1

	    do i = 1, CV_NCOEFF(cv) {
		jj = leftm1 + i
		sum = sum + XBASIS(xptr + i) * COEFF(cptr + jj)
	    }
	}
end

# semi-code for cveval

include "curfit.h"

# CVEVAL -- Procedure to evaluate curve at a given x

real procedure cveval (cv, x)

pointer	cv		# pointer to image descriptor structure
real	x		# x value

int	left, leftm1, i
pointer	cptr, xptr
real	sum

begin
	switch (CV_TYPE(cv)) {
	case CHEBYSHEV:
	    left = 1
	    call chebyshev (cv, x, XBASIS(CV_XBASIS(cv)))
	case LEGENDRE:
	    left = 1
	    call legendre (cv, x, XBASIS(CV_XBASIS(cv)))
	case L2SPLINE4:
	    call l2spline4 (cv, x, left, XBASIS(CV_XBASIS(cv)))
	}

	sum = 0.
	leftm1 = left - 1
	cptr = CV_COEFF(cv) - 1
	xptr = CV_XBASIS(cv) - 1
	do i = 1, CV_NCOEFF(cv) {
	    jj = leftm1 + i
	    sum = sum + XBASIS(xptr + i) * COEFF(cptr + jj)
	}

	return (sum)
end

# semi-code for cverrors

include "curfit.h"

# CVERRORS -- Procedure to calculate the standard deviation of the fit and the
# standard deviations of the coefficients

procedure cverrors (cv, rms, errors)

pointer	cv		# curve descriptor
real	rms		# standard deviation of data with respect to fit
real	errors[ARB]	# errors in coefficients

begin
	# calculate the variance
	rms = CV_YNORM(cv)
	cptr = CV_COEFF(cv) - 1
	vptr = CV_VECTOR(cv) - 1
	do i = 1, CV_NCOEFF(cv)
	    rms = rms - COEFF(cptr, i) * VECTOR(vptr, i)
	rms = rms / (CV_NPTS(cv) - CV_NCOEFF(cv))

	# calculate the standard deviations
	do i = 1, CV_NCOEFF(cv) {
	    do j = 1, CV_NCOEFF(cv)
		cov[j] = 0.
	    cov[i] = 1.
	    call choslv (CHO(CV_CHOFAC(cv)), CV_ORDER(cv),
	    		CV_NCOEFF(cv), cov, cov)
	    errors[i] = sqrt (cov[i] * rms)
	}

	rms = sqrt (rms)
end

# semi-code for CVFREE

# CVFREE -- Procedure to free the curve descriptor

procedure cvfree (cv)

pointer	cv

begin
	call sfree (cv)
end

include "curfit.h"

# LEGENDRE -- Procedure to calculate the Legendre functions.

procedure legendre (cv, x, basis)

pointer	cv
real	x
real	basis[ARB]

begin
	# normalize to the range x = -1. to 1.
	xnorm = (2. * x - CV_MAXMIN(cv)) / CV_RANGE(cv)

	b[1] = 1.0
	if (CV_ORDER(cv) == 1)
	    return

	b[2] = xnorm
	if (CV_ORDER(cv) == 2)
	    return

	do i = 3, CV_ORDER(cv) {
	    ri = i
	    b[i] = ((2.*ri-3.)*xnorm*b[i-1] - (ri-2.)*b[i-2]) / (ri-1.)
	}
end

# CHEBYSHEV -- Procedure to calculate Chebyshev polynomials.

procedure chebyshev (cv, x, basis)

real	x
int	order
real	basis[ARB]

begin
	# normalize to the range -1. to 1.
	xnorm = (2. * x - CV_MAXMIN(cv)) / CV_RANGE(cv)

	b[1] = 1.
	if (CV_ORDER(cv) == 1)
	    return

	b[2] = xnorm
	if (CV_ORDER(cv) == 2)
	    return

	do i = 3, CV_ORDER(cv) {
	    ri = i
	    b[i] = 2.*xnorm*b[i-1] - b[i-2]
	}
end

define	NPTS_SPLINE	401	# Number of points in the spline lookup table 
define	INTERVALS	100	# Number of intervals per spline knot

# L2SPLINE4 -- Procedure to calculate the cubic spline functions

procedure (cv, x, left, basis)

pointer	cv
real	x
int	left
real	basis[ARB]

real	table[NPTS_SPLINE]

# data table containing the spline
include "table.dat"

begin
	xnorm = (x - CV_XMIN(cv)) / CV_SPACING(cv)
	temp = min (int (xnorm), npieces - 1)
	left = temp +  1
	xnorm = xnorm - temp

	near = int ((1. - xnorm + 0.5) * INTERVALS) + 1
	basis[1] = table[near]
	near = table[near] + INTERVALS
	basis[2] = table[near]
	near = table[near] + INTERVALS
	basis[3] = table[near]
	near = table[near] + INTERVALS
	basis[4] = table[near]
end

# CHOFAC -- Routine to calculate the Cholesky factorization of a banded
# matrix.

procedure chofac (matrix, nbands, nrows, matfac, ier)

real	matrix[nbands, nrows]
int	nbands
int	nrows
real	matfac[nbands, nrows]
int	ier

begin
	ier = 0

	if (nrows == 1) {
	    if (matrix[1,1] .gt. 0.)
	        matfac[1,1] = 1./matrix[1,1]
	    return
	}

		
	# copy matrix into matfac
	do n = 1, nrows {
	    do j = 1, nbands
		matfac[j,n] = matrix[j,n]
	}

	do n = 1, nrows {

	    # test to see if matrix is singular
	    if (matfac[1,n] + matrix[1,n] <= matrix[1,n]) {
		do j = 1, nbands
		    w[j,n] = 0.
		ier = 1
		next
	    }

	    matfac[1,n] = 1./matfac[1,n]
	    imax = min (nbands - 1, nrows - n)
	    if (imax < 1)
		next

	    jmax = imax
	    do i = 1, imax {
		ratio = matfac[i+1,n] * matfac[1,n]
		do j = 1, jmax
		    matfac[j,n+i] = matfac[j,n+i] - matfac[j+i,n] * ratio
		jmax = jmax - 1
		matfac[i+1,n] = ratio
	    }
	}
end

# CHOSLV -- Solve the matrix whose Cholesky factorization was calculated in
# CHOFAC.

procedure choslv (matfac, nbands, nrows, vector, coeff)

real	matfac[nbands,nrows]
int	nbands
int	nrows
real	vector[nrows]
real	coeff[nrows]

begin
	if (nrows == 1) {
	    coeff[1] = vector[1] * matfac[1,1]
	    return
	}

	# copy vector to coefficients
	do i = 1, nrows
	    coeff[i] = vector[i]

	# forward substitution
	nbndm1 = nbands - 1
	do n = 1, nrows {
	    jmax = min (nbndm1, nrows - n)
	    if (jmax < 1)
		next
	    do j = 1, jmax
		coeff[j+n] = coeff[j+n] - matfac[j+1,n] * b[n]
	}

	# back substitution
	for (n = nrows; n > 0; n = n - 1) {
	    coeff[n] = coeff[n] * matfac[1,n]
	    jmax = min (nbndm1, nrows - 1)
	    if (jmax >= 1) {
		do j = 1, jmax
		    coeff[n] = coeff[n] - matfac[j+1,n] * coeff[j+n]
	    }
	}

end