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interpol.c
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1998-11-16
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#ifndef lint
static char *RCSid = "$Id: interpol.c,v 1.29 1998/04/14 00:15:45 drd Exp $";
#endif
/* GNUPLOT - interpol.c */
/*[
* Copyright 1986 - 1993, 1998 Thomas Williams, Colin Kelley
*
* Permission to use, copy, and distribute this software and its
* documentation for any purpose with or without fee is hereby granted,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation.
*
* Permission to modify the software is granted, but not the right to
* distribute the complete modified source code. Modifications are to
* be distributed as patches to the released version. Permission to
* distribute binaries produced by compiling modified sources is granted,
* provided you
* 1. distribute the corresponding source modifications from the
* released version in the form of a patch file along with the binaries,
* 2. add special version identification to distinguish your version
* in addition to the base release version number,
* 3. provide your name and address as the primary contact for the
* support of your modified version, and
* 4. retain our contact information in regard to use of the base
* software.
* Permission to distribute the released version of the source code along
* with corresponding source modifications in the form of a patch file is
* granted with same provisions 2 through 4 for binary distributions.
*
* This software is provided "as is" without express or implied warranty
* to the extent permitted by applicable law.
]*/
/*
* C-Source file identification Header
*
* This file belongs to a project which is:
*
* done 1993 by MGR-Software, Asgard (Lars Hanke)
* written by Lars Hanke
*
* Contact me via:
*
* InterNet: mgr@asgard.bo.open.de
* FIDO: Lars Hanke @ 2:243/4802.22 (as long as they keep addresses)
*
**************************************************************************
*
* Project: gnuplot
* Module:
* File: interpol.c
*
* Revisor: Lars Hanke
* Revised: 26/09/93
* Revision: 1.0
*
**************************************************************************
*
* LEGAL
* This module is part of gnuplot and distributed under whatever terms
* gnuplot is or will be published, unless exclusive rights are claimed.
*
* DESCRIPTION
* Supplies 2-D data interpolation and approximation routines
*
* IMPORTS
* plot.h
* - cp_extend()
* - structs: curve_points, coordval, coordinate
*
* setshow.h
* - samples, is_log_x, base_log_x, xmin, xmax, autoscale_lx
* - plottypes
*
* proto.h
* - solve_tri_diag()
* - typedef tri_diag
*
* EXPORTS
* gen_interp()
* sort_points()
* cp_implode()
*
* BUGS and TODO
* I would really have liked to use Gershon Elbers contouring code for
* all the stuff done here, but I failed. So I used my own code.
* If somebody is able to consolidate Gershon's code for this purpose
* a lot of gnuplot users would be very happy - due to memory problems.
*
**************************************************************************
*
* HISTORY
* Changes:
* Nov 24, 1995 Markus Schuh (M.Schuh@meteo.uni-koeln.de):
* changed the algorithm for csplines
* added algorithm for approximation csplines
* copied point storage and range fix from plot2d.c
*
* Dec 12, 1995 David Denholm
* oops - at the time this is called, stored co-ords are
* internal (ie maybe log of data) but min/max are in
* user co-ordinates.
* Work with min and max of internal co-ords, and
* check at the end whether external min and max need to
* be increased. (since samples is typically 100 ; we
* dont want to take more logs than necessary)
* Also, need to take into account which axes are active
*
* Jun 30, 1996 Jens Emmerich
* implemented handling of UNDEFINED points
*/
#include "plot.h"
#include "setshow.h"
/* in order to support multiple axes, and to simplify ranging in
* parametric plots, we use arrays to store some things. For 2d plots,
* elements are z=0,y1=1,x1=2,z2=4,y2=5,x2=6 these are given symbolic
* names in plot.h
*/
extern double min_array[AXIS_ARRAY_SIZE];
extern double max_array[AXIS_ARRAY_SIZE];
extern int auto_array[AXIS_ARRAY_SIZE];
extern TBOOLEAN log_array[AXIS_ARRAY_SIZE];
extern double base_array[AXIS_ARRAY_SIZE];
extern double log_base_array[AXIS_ARRAY_SIZE];
#define Inc_c_token if (++c_token >= num_tokens) \
int_error ("Syntax error", c_token);
/*
* IMHO, code is getting too cluttered with repeated chunks of
* code. Some macros to simplify, I hope.
*
* do { } while(0) is comp.lang.c recommendation for complex macros
* also means that break can be specified as an action, and it will
*
*/
/* store VALUE or log(VALUE) in STORE, set TYPE as appropriate
* Do OUT_ACTION or UNDEF_ACTION as appropriate
* adjust range provided type is INRANGE (ie dont adjust y if x is outrange
* VALUE must not be same as STORE
*/
#define STORE_AND_FIXUP_RANGE(STORE, VALUE, TYPE, MIN, MAX, AUTO, OUT_ACTION, UNDEF_ACTION)\
do { STORE=VALUE; \
if (TYPE != INRANGE) break; /* dont set y range if x is outrange, for example */ \
if ( VALUE<MIN ) { \
if (AUTO & 1) MIN=VALUE; else { TYPE=OUTRANGE; OUT_ACTION; break; } \
} \
if ( VALUE>MAX ) {\
if (AUTO & 2) MAX=VALUE; else { TYPE=OUTRANGE; OUT_ACTION; } \
} \
} while(0)
#define UPDATE_RANGE(TEST,OLD,NEW,AXIS) \
do { if (TEST) { \
if (log_array[AXIS]) OLD = pow(base_array[AXIS], NEW); else OLD = NEW; \
} \
} while(0)
/* use this instead empty macro arguments to work around NeXT cpp bug */
/* if this fails on any system, we might use ((void)0) */
#define NOOP /* */
#define spline_coeff_size 4
typedef double spline_coeff[spline_coeff_size];
typedef double five_diag[5];
static int next_curve __PROTO((struct curve_points * plot, int *curve_start));
static int num_curves __PROTO((struct curve_points * plot));
static double *cp_binomial __PROTO((int points));
GP_INLINE static double s_pow __PROTO((double base, unsigned int exponent));
static void eval_bezier __PROTO((struct curve_points * cp, int first_point, int num_points, double sr, coordval * px, coordval * py, double *c));
static void do_bezier __PROTO((struct curve_points * cp, double *bc, int first_point, int num_points, struct coordinate * dest));
static int solve_five_diag __PROTO((five_diag m[], double r[], double x[], int n));
static spline_coeff *cp_approx_spline __PROTO((struct curve_points * plot, int first_point, int num_points));
static spline_coeff *cp_tridiag __PROTO((struct curve_points * plot, int first_point, int num_points));
static void do_cubic __PROTO((struct curve_points * plot, spline_coeff * sc, int first_point, int num_points, struct coordinate * dest));
static int compare_points __PROTO((struct coordinate * p1, struct coordinate * p2));
/*
* position curve_start to index the next non-UNDEFINDED point,
* start search at initial curve_start,
* return number of non-UNDEFINDED points from there on,
* if no more valid points are found, curve_start is set
* to plot->p_count and 0 is returned
*/
static int next_curve(plot, curve_start)
struct curve_points *plot;
int *curve_start;
{
int curve_length;
/* Skip undefined points */
while (*curve_start < plot->p_count
&& plot->points[*curve_start].type == UNDEFINED) {
(*curve_start)++;
};
curve_length = 0;
/* curve_length is first used as an offset, then the correkt # points */
while ((*curve_start) + curve_length < plot->p_count
&& plot->points[(*curve_start) + curve_length].type != UNDEFINED) {
curve_length++;
};
return (curve_length);
}
/*
* determine the number of curves in plot->points, separated by
* UNDEFINED points
*/
static int num_curves(plot)
struct curve_points *plot;
{
int curves;
int first_point;
int num_points;
first_point = 0;
curves = 0;
while ((num_points = next_curve(plot, &first_point)) > 0) {
curves++;
first_point += num_points;
}
return (curves);
}
/*
* build up a cntr_struct list from curve_points
* this funtion is only used for the alternate entry point to
* Gershon's code and thus commented out
***deleted***
*/
/*
* cp_binomial() computes the binomial coefficients needed for BEZIER stuff
* and stores them into an array which is hooked to sdat.
* (MGR 1992)
*/
static double *cp_binomial(points)
int points;
{
register double *coeff;
register int n, k;
int e;
e = points; /* well we're going from k=0 to k=p_count-1 */
coeff = (double *) gp_alloc(e * sizeof(double), "bezier coefficients");
n = points - 1;
e = n / 2;
coeff[0] = 1.0;
for (k = 0; k < e; k++) {
coeff[k + 1] = coeff[k] * ((double) (n - k)) / ((double) (k + 1));
}
for (k = n; k >= e; k--)
coeff[k] = coeff[n - k];
return (coeff);
}
/* This is a subfunction of do_bezier() for BEZIER style computations.
* It is passed the stepration (STEP/MAXSTEPS) and the addresses of
* the double values holding the next x and y coordinates.
* (MGR 1992)
*/
/*
* well, this routine runs faster with the 68040 striptease FPU
* and it handles zeroes correctly - there had been some trouble with TC
*/
GP_INLINE static double s_pow(base, exponent)
double base;
unsigned int exponent;
{
double y;
if (exponent == 0)
return (1.0);
if (base == 0.0)
return (0.0);
/* consider i in binary = abcd
* x^i = x^(8a+4b+2c+d) = x^8a * x^4b * x^2b * x^d
* = a?x^2^2^2:1 * b?x^2^2:1 + ...
* so for each bit in exponent, square x, multiplying it into accumulator
*
*/
y = 1;
while (exponent) {
if (exponent & 1)
y *= base;
base *= base;
/* if exponent was signed, this could be trouble ! */
exponent >>= 1;
}
return (y);
}
static void eval_bezier(cp, first_point, num_points, sr, px, py, c)
struct curve_points *cp;
int first_point; /* where to start in plot->points (to find x-range) */
int num_points; /* to determine end in plot->points */
double sr;
coordval *px;
coordval *py;
double *c;
{
unsigned int n = num_points - 1;
/* HBB 980308: added 'GPHUGE' tag for DOS */
struct coordinate GPHUGE *this_points;
this_points = (cp->points) + first_point;
if (sr == 0.0) {
*px = this_points[0].x;
*py = this_points[0].y;
} else if (sr == 1.0) {
*px = this_points[n].x;
*py = this_points[n].y;
} else {
unsigned int i;
double lx = 0.0, ly = 0.0;
double sr_to_the_i = 1.0;
double dsr_to_the_di = s_pow(1 - sr, n);
double reciprocal_dsr = 1.0 / (1 - sr);
for (i = 0; i <= n; i++) {
double u = c[i] * sr_to_the_i * s_pow(1 - sr, n - i);
lx += this_points[i].x * u;
ly += this_points[i].y * u;
sr_to_the_i *= sr;
dsr_to_the_di *= reciprocal_dsr;
}
*px = lx;
*py = ly;
}
}
/*
* generate a new set of coordinates representing the bezier curve and
* set it to the plot
*/
static void do_bezier(cp, bc, first_point, num_points, dest)
struct curve_points *cp;
double *bc;
int first_point; /* where to start in plot->points */
int num_points; /* to determine end in plot->points */
struct coordinate *dest; /* where to put the interpolated data */
{
int i;
coordval x, y;
int xaxis = cp->x_axis;
int yaxis = cp->y_axis;
/* min and max in internal (eg logged) co-ordinates. We update
* these, then update the external extrema in user co-ordinates
* at the end.
*/
double ixmin, ixmax, iymin, iymax;
double sxmin, sxmax, symin, symax; /* starting values of above */
if (log_array[xaxis]) {
ixmin = sxmin = log(min_array[xaxis]) / log_base_array[xaxis];
ixmax = sxmax = log(max_array[xaxis]) / log_base_array[xaxis];
} else {
ixmin = sxmin = min_array[xaxis];
ixmax = sxmax = max_array[xaxis];
}
if (log_array[yaxis]) {
iymin = symin = log(min_array[yaxis]) / log_base_array[yaxis];
iymax = symax = log(max_array[yaxis]) / log_base_array[yaxis];
} else {
iymin = symin = min_array[yaxis];
iymax = symax = max_array[yaxis];
}
for (i = 0; i < samples; i++) {
eval_bezier(cp, first_point, num_points, (double) i / (double) (samples - 1), &x, &y, bc);
/* now we have to store the points and adjust the ranges */
dest[i].type = INRANGE;
STORE_AND_FIXUP_RANGE(dest[i].x, x, dest[i].type, ixmin, ixmax, auto_array[xaxis], NOOP, continue);
STORE_AND_FIXUP_RANGE(dest[i].y, y, dest[i].type, iymin, iymax, auto_array[yaxis], NOOP, NOOP);
dest[i].xlow = dest[i].xhigh = dest[i].x;
dest[i].ylow = dest[i].yhigh = dest[i].y;
dest[i].z = -1;
}
UPDATE_RANGE(ixmax > sxmax, max_array[xaxis], ixmax, xaxis);
UPDATE_RANGE(ixmin < sxmin, min_array[xaxis], ixmin, xaxis);
UPDATE_RANGE(iymax > symax, max_array[yaxis], iymax, yaxis);
UPDATE_RANGE(iymin < symin, min_array[yaxis], iymin, yaxis);
}
/*
* call contouring routines -- main entry
*/
/*
* it should be like this, but it doesn't run. If you find out why,
* contact me: mgr@asgard.bo.open.de or Lars Hanke 2:243/4802.22@fidonet
*
* Well, all this had originally been inside contour.c, so maybe links
* to functions and of contour.c are broken.
* ***deleted***
* end of unused entry point to Gershon's code
*
*/
/*
* Solve five diagonal linear system equation. The five diagonal matrix is
* defined via matrix M, right side is r, and solution X i.e. M * X = R.
* Size of system given in n. Return TRUE if solution exist.
* G. Engeln-Muellges/ F.Reutter:
* "Formelsammlung zur Numerischen Mathematik mit Standard-FORTRAN-Programmen"
* ISBN 3-411-01677-9
*
* / m02 m03 m04 0 0 0 0 . . . \ / x0 \ / r0 \
* I m11 m12 m13 m14 0 0 0 . . . I I x1 I I r1 I
* I m20 m21 m22 m23 m24 0 0 . . . I * I x2 I = I r2 I
* I 0 m30 m31 m32 m33 m34 0 . . . I I x3 I I r3 I
* . . . . . . . . . . . .
* \ m(n-3)0 m(n-2)1 m(n-1)2 / \x(n-1)/ \r(n-1)/
*
*/
static int solve_five_diag(m, r, x, n)
five_diag m[];
double r[], x[];
int n;
{
int i;
five_diag *hv;
hv = (five_diag *) gp_alloc((n + 1) * sizeof(five_diag), "five_diag help vars");
hv[0][0] = m[0][2];
if (hv[0][0] == 0) {
free(hv);
return FALSE;
}
hv[0][1] = m[0][3] / hv[0][0];
hv[0][2] = m[0][4] / hv[0][0];
hv[1][3] = m[1][1];
hv[1][0] = m[1][2] - hv[1][3] * hv[0][1];
if (hv[1][0] == 0) {
free(hv);
return FALSE;
}
hv[1][1] = (m[1][3] - hv[1][3] * hv[0][2]) / hv[1][0];
hv[1][2] = m[1][4] / hv[1][0];
for (i = 2; i <= n - 1; i++) {
hv[i][3] = m[i][1] - m[i][0] * hv[i - 2][1];
hv[i][0] = m[i][2] - m[i][0] * hv[i - 2][2] - hv[i][3] * hv[i - 1][1];
if (hv[i][0] == 0) {
free(hv);
return FALSE;
}
hv[i][1] = (m[i][3] - hv[i][3] * hv[i - 1][2]) / hv[i][0];
hv[i][2] = m[i][4] / hv[i][0];
}
hv[0][4] = 0;
hv[1][4] = r[0] / hv[0][0];
for (i = 1; i <= n - 1; i++) {
hv[i + 1][4] = (r[i] - m[i][0] * hv[i - 1][4] - hv[i][3] * hv[i][4]) / hv[i][0];
}
x[n - 1] = hv[n][4];
x[n - 2] = hv[n - 1][4] - hv[n - 2][1] * x[n - 1];
for (i = n - 3; i >= 0; i--)
x[i] = hv[i + 1][4] - hv[i][1] * x[i + 1] - hv[i][2] * x[i + 2];
free(hv);
return TRUE;
}
/*
* Calculation of approximation cubic splines
* Input: x[i], y[i], weights z[i]
*
* Returns matrix of spline coefficients
*/
static spline_coeff *cp_approx_spline(plot, first_point, num_points)
struct curve_points *plot;
int first_point; /* where to start in plot->points */
int num_points; /* to determine end in plot->points */
{
spline_coeff *sc;
five_diag *m;
int xaxis = plot->x_axis;
int yaxis = plot->y_axis;
double *r, *x, *h, *xp, *yp;
/* HBB 980308: added 'GPHUGE' tag */
struct coordinate GPHUGE *this_points;
int i;
sc = (spline_coeff *) gp_alloc((num_points) * sizeof(spline_coeff),
"spline matrix");
if (num_points < 4)
int_error("Can't calculate approximation splines, need at least 4 points", NO_CARET);
this_points = (plot->points) + first_point;
for (i = 0; i <= num_points - 1; i++)
if (this_points[i].z <= 0)
int_error("Can't calculate approximation splines, all weights have to be > 0", NO_CARET);
m = (five_diag *) gp_alloc((num_points - 2) * sizeof(five_diag), "spline help matrix");
r = (double *) gp_alloc((num_points - 2) * sizeof(double), "spline right side");
x = (double *) gp_alloc((num_points - 2) * sizeof(double), "spline solution vector");
h = (double *) gp_alloc((num_points - 1) * sizeof(double), "spline help vector");
xp = (double *) gp_alloc((num_points) * sizeof(double), "x pos");
yp = (double *) gp_alloc((num_points) * sizeof(double), "y pos");
/* KB 981107: With logarithmic axis first convert back to linear scale */
if (log_array[xaxis]) {
for (i = 0; i <= num_points - 1; i++)
xp[i] = exp(this_points[i].x * log_base_array[xaxis]);
} else {
for (i = 0; i <= num_points - 1; i++)
xp[i] = this_points[i].x;
}
if (log_array[yaxis]) {
for (i = 0; i <= num_points - 1; i++)
yp[i] = exp(this_points[i].y * log_base_array[yaxis]);
} else {
for (i = 0; i <= num_points - 1; i++)
yp[i] = this_points[i].y;
}
for (i = 0; i <= num_points - 2; i++)
h[i] = xp[i + 1] - xp[i];
/* set up the matrix and the vector */
for (i = 0; i <= num_points - 3; i++) {
r[i] = 3 * ((yp[i + 2] - yp[i + 1]) / h[i + 1]
- (yp[i + 1] - yp[i]) / h[i]);
if (i < 2)
m[i][0] = 0;
else
m[i][0] = 6 / this_points[i].z / h[i - 1] / h[i];
if (i < 1)
m[i][1] = 0;
else
m[i][1] = h[i] - 6 / this_points[i].z / h[i] * (1 / h[i - 1] + 1 / h[i])
- 6 / this_points[i + 1].z / h[i] * (1 / h[i] + 1 / h[i + 1]);
m[i][2] = 2 * (h[i] + h[i + 1])
+ 6 / this_points[i].z / h[i] / h[i]
+ 6 / this_points[i + 1].z * (1 / h[i] + 1 / h[i + 1]) * (1 / h[i] + 1 / h[i + 1])
+ 6 / this_points[i + 2].z / h[i + 1] / h[i + 1];
if (i > num_points - 4)
m[i][3] = 0;
else
m[i][3] = h[i + 1] - 6 / this_points[i + 1].z / h[i + 1] * (1 / h[i] + 1 / h[i + 1])
- 6 / this_points[i + 2].z / h[i + 1] * (1 / h[i + 1] + 1 / h[i + 2]);
if (i > num_points - 5)
m[i][4] = 0;
else
m[i][4] = 6 / this_points[i + 2].z / h[i + 1] / h[i + 2];
}
/* solve the matrix */
if (!solve_five_diag(m, r, x, num_points - 2)) {
free(h);
free(x);
free(r);
free(m);
free(xp);
free(yp);
int_error("Can't calculate approximation splines", NO_CARET);
}
sc[0][2] = 0;
for (i = 1; i <= num_points - 2; i++)
sc[i][2] = x[i - 1];
sc[num_points - 1][2] = 0;
sc[0][0] = yp[0] + 2 / this_points[0].z / h[0] * (sc[0][2] - sc[1][2]);
for (i = 1; i <= num_points - 2; i++)
sc[i][0] = yp[i] - 2 / this_points[i].z *
(sc[i - 1][2] / h[i - 1]
- sc[i][2] * (1 / h[i - 1] + 1 / h[i])
+ sc[i + 1][2] / h[i]);
sc[num_points - 1][0] = yp[num_points - 1]
- 2 / this_points[num_points - 1].z / h[num_points - 2]
* (sc[num_points - 2][2] - sc[num_points - 1][2]);
for (i = 0; i <= num_points - 2; i++) {
sc[i][1] = (sc[i + 1][0] - sc[i][0]) / h[i]
- h[i] / 3 * (sc[i + 1][2] + 2 * sc[i][2]);
sc[i][3] = (sc[i + 1][2] - sc[i][2]) / 3 / h[i];
}
free(h);
free(x);
free(r);
free(m);
free(xp);
free(yp);
return (sc);
}
/*
* Calculation of cubic splines
*
* This can be treated as a special case of approximation cubic splines, with
* all weights -> infinity.
*
* Returns matrix of spline coefficients
*/
static spline_coeff *cp_tridiag(plot, first_point, num_points)
struct curve_points *plot;
int first_point, num_points;
{
spline_coeff *sc;
tri_diag *m;
int xaxis = plot->x_axis;
int yaxis = plot->y_axis;
double *r, *x, *h, *xp, *yp;
/* HBB 980308: added 'GPHUGE' tag */
struct coordinate GPHUGE *this_points;
int i;
if (num_points < 3)
int_error("Can't calculate splines, need at least 3 points", NO_CARET);
this_points = (plot->points) + first_point;
sc = (spline_coeff *) gp_alloc((num_points) * sizeof(spline_coeff), "spline matrix");
m = (tri_diag *) gp_alloc((num_points - 2) * sizeof(tri_diag), "spline help matrix");
r = (double *) gp_alloc((num_points - 2) * sizeof(double), "spline right side");
x = (double *) gp_alloc((num_points - 2) * sizeof(double), "spline solution vector");
h = (double *) gp_alloc((num_points - 1) * sizeof(double), "spline help vector");
xp = (double *) gp_alloc((num_points) * sizeof(double), "x pos");
yp = (double *) gp_alloc((num_points) * sizeof(double), "y pos");
/* KB 981107: With logarithmic axis first convert back to linear scale */
if (log_array[xaxis]) {
for (i = 0; i <= num_points - 1; i++)
xp[i] = exp(this_points[i].x * log_base_array[xaxis]);
} else {
for (i = 0; i <= num_points - 1; i++)
xp[i] = this_points[i].x;
}
if (log_array[yaxis]) {
for (i = 0; i <= num_points - 1; i++)
yp[i] = exp(this_points[i].y * log_base_array[yaxis]);
} else {
for (i = 0; i <= num_points - 1; i++)
yp[i] = this_points[i].y;
}
for (i = 0; i <= num_points - 2; i++)
h[i] = xp[i + 1] - xp[i];
/* set up the matrix and the vector */
for (i = 0; i <= num_points - 3; i++) {
r[i] = 3 * ((yp[i + 2] - yp[i + 1]) / h[i + 1]
- (yp[i + 1] - yp[i]) / h[i]);
if (i < 1)
m[i][0] = 0;
else
m[i][0] = h[i];
m[i][1] = 2 * (h[i] + h[i + 1]);
if (i > num_points - 4)
m[i][2] = 0;
else
m[i][2] = h[i + 1];
}
/* solve the matrix */
if (!solve_tri_diag(m, r, x, num_points - 2)) {
free(h);
free(x);
free(r);
free(m);
free(xp);
free(yp);
int_error("Can't calculate cubic splines", NO_CARET);
}
sc[0][2] = 0;
for (i = 1; i <= num_points - 2; i++)
sc[i][2] = x[i - 1];
sc[num_points - 1][2] = 0;
for (i = 0; i <= num_points - 1; i++)
sc[i][0] = yp[i];
for (i = 0; i <= num_points - 2; i++) {
sc[i][1] = (sc[i + 1][0] - sc[i][0]) / h[i]
- h[i] / 3 * (sc[i + 1][2] + 2 * sc[i][2]);
sc[i][3] = (sc[i + 1][2] - sc[i][2]) / 3 / h[i];
}
free(h);
free(x);
free(r);
free(m);
free(xp);
free(yp);
return (sc);
}
static void do_cubic(plot, sc, first_point, num_points, dest)
struct curve_points *plot; /* still containes old plot->points */
spline_coeff *sc; /* generated by cp_tridiag */
int first_point; /* where to start in plot->points */
int num_points; /* to determine end in plot->points */
struct coordinate *dest; /* where to put the interpolated data */
{
double xdiff, temp, x, y;
int i, l;
int xaxis = plot->x_axis;
int yaxis = plot->y_axis;
/* HBB 980308: added 'GPHUGE' tag */
struct coordinate GPHUGE *this_points;
/* min and max in internal (eg logged) co-ordinates. We update
* these, then update the external extrema in user co-ordinates
* at the end.
*/
double ixmin, ixmax, iymin, iymax;
double sxmin, sxmax, symin, symax; /* starting values of above */
if (log_array[xaxis]) {
ixmin = sxmin = log(min_array[xaxis]) / log_base_array[xaxis];
ixmax = sxmax = log(max_array[xaxis]) / log_base_array[xaxis];
} else {
ixmin = sxmin = min_array[xaxis];
ixmax = sxmax = max_array[xaxis];
}
if (log_array[yaxis]) {
iymin = symin = log(min_array[yaxis]) / log_base_array[yaxis];
iymax = symax = log(max_array[yaxis]) / log_base_array[yaxis];
} else {
iymin = symin = min_array[yaxis];
iymax = symax = max_array[yaxis];
}
this_points = (plot->points) + first_point;
l = 0;
xdiff = (this_points[num_points - 1].x - this_points[0].x) / (samples - 1);
for (i = 0; i < samples; i++) {
x = this_points[0].x + i * xdiff;
while ((x >= this_points[l + 1].x) && (l < num_points - 2))
l++;
/* KB 981107: With logarithmic x axis the values were converted back to linear */
/* scale before calculating the coefficients. Use exponential for log x values. */
if (log_array[xaxis]) {
temp = exp(x * log_base_array[xaxis]) - exp(this_points[l].x * log_base_array[xaxis]);
y = ((sc[l][3] * temp + sc[l][2]) * temp + sc[l][1]) * temp + sc[l][0];
} else {
temp = x - this_points[l].x;
y = ((sc[l][3] * temp + sc[l][2]) * temp + sc[l][1]) * temp + sc[l][0];
}
/* With logarithmic y axis, we need to convert from linear to log scale now. */
if (log_array[yaxis]) {
if (y > 0.)
y = log(y) / log_base_array[yaxis];
else
y = symin - (symax - symin);
}
dest[i].type = INRANGE;
STORE_AND_FIXUP_RANGE(dest[i].x, x, dest[i].type, ixmin, ixmax, auto_array[xaxis], NOOP, continue);
STORE_AND_FIXUP_RANGE(dest[i].y, y, dest[i].type, iymin, iymax, auto_array[yaxis], NOOP, NOOP);
dest[i].xlow = dest[i].xhigh = dest[i].x;
dest[i].ylow = dest[i].yhigh = dest[i].y;
dest[i].z = -1;
}
UPDATE_RANGE(ixmax > sxmax, max_array[xaxis], ixmax, xaxis);
UPDATE_RANGE(ixmin < sxmin, min_array[xaxis], ixmin, xaxis);
UPDATE_RANGE(iymax > symax, max_array[yaxis], iymax, yaxis);
UPDATE_RANGE(iymin < symin, min_array[yaxis], iymin, yaxis);
}
/*
* This is the main entry point used. As stated in the header, it is fine,
* but I'm not too happy with it.
*/
void gen_interp(plot)
struct curve_points *plot;
{
spline_coeff *sc;
double *bc;
struct coordinate *new_points;
int i, curves;
int first_point, num_points;
curves = num_curves(plot);
new_points = (struct coordinate *) gp_alloc((samples + 1) * curves * sizeof(struct coordinate), "interpolation table");
first_point = 0;
for (i = 0; i < curves; i++) {
num_points = next_curve(plot, &first_point);
switch (plot->plot_smooth) {
case CSPLINES:
sc = cp_tridiag(plot, first_point, num_points);
do_cubic(plot, sc, first_point, num_points,
new_points + i * (samples + 1));
free(sc);
break;
case ACSPLINES:
sc = cp_approx_spline(plot, first_point, num_points);
do_cubic(plot, sc, first_point, num_points,
new_points + i * (samples + 1));
free(sc);
break;
case BEZIER:
case SBEZIER:
bc = cp_binomial(num_points);
do_bezier(plot, bc, first_point, num_points,
new_points + i * (samples + 1));
free((char *) bc);
break;
default: /* keep gcc -Wall quiet */
;
}
new_points[(i + 1) * (samples + 1) - 1].type = UNDEFINED;
first_point += num_points;
}
free(plot->points);
plot->points = new_points;
plot->p_max = curves * (samples + 1);
plot->p_count = plot->p_max - 1;
return;
}
/*
* sort_points
*
* sort data succession for further evaluation by plot_splines, etc.
* This routine is mainly introduced for compilers *NOT* supporting the
* UNIX qsort() routine. You can then easily replace it by more convenient
* stuff for your compiler.
* (MGR 1992)
*/
static int compare_points(p1, p2)
struct coordinate *p1;
struct coordinate *p2;
{
if (p1->x > p2->x)
return (1);
if (p1->x < p2->x)
return (-1);
return (0);
}
void sort_points(plot)
struct curve_points *plot;
{
int first_point, num_points;
first_point = 0;
while ((num_points = next_curve(plot, &first_point)) > 0) {
/* Sort this set of points, does qsort handle 1 point correctly? */
qsort((char *) (plot->points + first_point), num_points,
sizeof(struct coordinate), (sortfunc) compare_points);
first_point += num_points;
}
return;
}
/*
* cp_implode() if averaging is selected this function computes the new
* entries and shortens the whole thing to the necessary
* size
* MGR Addendum
*/
void cp_implode(cp)
struct curve_points *cp;
{
int first_point, num_points;
int i, j, k;
double x, y, sux, slx, suy, sly;
enum coord_type dot;
j = 0;
first_point = 0;
while ((num_points = next_curve(cp, &first_point)) > 0) {
k = 0;
for (i = first_point; i < first_point + num_points; i++) {
if (!k) {
x = cp->points[i].x;
y = cp->points[i].y;
sux = cp->points[i].xhigh;
slx = cp->points[i].xlow;
suy = cp->points[i].yhigh;
sly = cp->points[i].ylow;
dot = INRANGE;
if (cp->points[i].type != INRANGE)
dot = UNDEFINED; /* This means somthing other than usual *//* just signal to check if INRANGE */
k = 1;
} else if (cp->points[i].x == x) {
y += cp->points[i].y;
sux += cp->points[i].xhigh;
slx += cp->points[i].xlow;
suy += cp->points[i].yhigh;
sly += cp->points[i].ylow;
if (cp->points[i].type != INRANGE)
dot = UNDEFINED;
k++;
} else {
cp->points[j].x = x;
cp->points[j].y = y / (double) k;
cp->points[j].xhigh = sux / (double) k;
cp->points[j].xlow = slx / (double) k;
cp->points[j].yhigh = suy / (double) k;
cp->points[j].ylow = sly / (double) k;
cp->points[j].type = INRANGE;
if (dot != INRANGE) {
if ((cp->points[j].x > xmax) || (cp->points[j].x < xmin))
cp->points[j].type = OUTRANGE;
else if (!autoscale_ly) {
if ((cp->points[j].y > ymax) || (cp->points[j].y < ymin))
cp->points[j].type = OUTRANGE;
} else
cp->points[j].type = INRANGE;
}
j++; /* next valid entry */
k = 0; /* to read */
i--; /* from this (-> last after for(;;)) entry */
}
}
if (k) {
cp->points[j].x = x;
cp->points[j].y = y / (double) k;
cp->points[j].xhigh = sux / (double) k;
cp->points[j].xlow = slx / (double) k;
cp->points[j].yhigh = suy / (double) k;
cp->points[j].ylow = sly / (double) k;
cp->points[j].type = INRANGE;
if (dot != INRANGE) {
if ((cp->points[j].x > xmax) || (cp->points[j].x < xmin))
cp->points[j].type = OUTRANGE;
else if (!autoscale_ly) {
if ((cp->points[j].y > ymax) || (cp->points[j].y < ymin))
cp->points[j].type = OUTRANGE;
} else
cp->points[j].type = INRANGE;
}
j++; /* next valid entry */
}
/* insert invalid point to separate curves */
if (j < cp->p_count) {
cp->points[j].type = UNDEFINED;
j++;
}
first_point += num_points;
} /* end while */
cp->p_count = j;
cp_extend(cp, j);
}