File: fit.c

package info (click to toggle)
gnuplot 3.7.1p1-4
  • links: PTS
  • area: main
  • in suites: potato
  • size: 5,808 kB
  • ctags: 4,418
  • sloc: ansic: 43,279; lisp: 661; makefile: 647; asm: 539; sh: 416; objc: 379; csh: 297; pascal: 194; perl: 138
file content (1650 lines) | stat: -rw-r--r-- 46,786 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
#ifndef lint
static char *RCSid = "$Id: fit.c,v 1.23.2.3 1999/10/01 18:22:14 lhecking Exp $";
#endif

/*
 *    Nonlinear least squares fit according to the
 *      Marquardt-Levenberg-algorithm
 *
 *      added as Patch to Gnuplot (v3.2 and higher)
 *      by Carsten Grammes
 *      Experimental Physics, University of Saarbruecken, Germany
 *
 *      Internet address: cagr@rz.uni-sb.de
 *
 *      Copyright of this module:  1993, 1998  Carsten Grammes
 *
 *      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.
 *
 *      This software is provided "as is" without express or implied warranty.
 *
 *      930726:     Recoding of the Unix-like raw console I/O routines by:
 *                  Michele Marziani (marziani@ferrara.infn.it)
 * drd: start unitialised variables at 1 rather than NEARLY_ZERO
 *  (fit is more likely to converge if started from 1 than 1e-30 ?)
 *
 * HBB (Broeker@physik.rwth-aachen.de) : fit didn't calculate the errors
 * in the 'physically correct' (:-) way, if a third data column containing
 * the errors (or 'uncertainties') of the input data was given. I think
 * I've fixed that, but I'm not sure I really understood the M-L-algo well
 * enough to get it right. I deduced my change from the final steps of the
 * equivalent algorithm for the linear case, which is much easier to
 * understand. (I also made some minor, mostly cosmetic changes)
 *
 * HBB (again): added error checking for negative covar[i][i] values and
 * for too many parameters being specified.
 *
 * drd: allow 3d fitting. Data value is now called fit_z internally,
 * ie a 2d fit is z vs x, and a 3d fit is z vs x and y.
 *
 * Lars Hecking : review update command, for VMS in particular, where
 * it is not necessary to rename the old file.
 *
 * HBB, 971023: lifted fixed limit on number of datapoints, and number
 * of parameters.
 */


#define FIT_MAIN

#include <signal.h>

#include "plot.h"
#include "matrix.h"
#include "fit.h"
#include "setshow.h"		/* for load_range */
#include "alloc.h"

#if defined(MSDOS) || defined(DOS386)	/* non-blocking IO stuff */
# include <io.h>
# ifndef _Windows		/* WIN16 does define MSDOS .... */
#  include <conio.h>
# endif
# include <dos.h>
#else /* !(MSDOS || DOS386) */
# ifndef VMS
#  include <fcntl.h>
# endif				/* !VMS */
#endif /* !(MSDOS || DOS386) */

#if defined(ATARI) || defined(MTOS)
# define getchx() Crawcin()
static int kbhit(void);
#endif

#define STANDARD    stderr	/* compatible with gnuplot philosophy */

#define BACKUP_SUFFIX ".old"


/* access external global variables  (ought to make a globals.h someday) */

extern struct udft_entry *dummy_func;
extern char dummy_var[MAX_NUM_VAR][MAX_ID_LEN+1];
extern char c_dummy_var[MAX_NUM_VAR][MAX_ID_LEN+1];
extern int c_token;
extern int df_datum, df_line_number;

/* following 2 external arrays are needed to use time data */
extern int datatype[];
extern int df_timecol[];

enum marq_res {
    OK, ERROR, BETTER, WORSE
};
typedef enum marq_res marq_res_t;

#ifdef INFINITY
# undef INFINITY
#endif

#define INFINITY    1e30
#define NEARLY_ZERO 1e-30

/* create new variables with this value (was NEARLY_ZERO) */
#define INITIAL_VALUE 1.0

/* Relative change for derivatives */
#define DELTA	    0.001

#define MAX_DATA    2048
#define MAX_PARAMS  32
#define MAX_LAMBDA  1e20
#define MIN_LAMBDA  1e-20
#define LAMBDA_UP_FACTOR 10
#define LAMBDA_DOWN_FACTOR 10

#if defined(MSDOS) || defined(OS2) || defined(DOS386)
# define PLUSMINUS   "\xF1"	/* plusminus sign */
#else
# define PLUSMINUS   "+/-"
#endif

#define LASTFITCMDLENGTH 511

/* HBB 971023: new, allow for dynamic adjustment of these: */
static int max_data;
static int max_params;

static double epsilon = 1e-5;	/* convergence limit */
static int maxiter = 0;		/* HBB 970304: maxiter patch */

static char fit_script[128];
static char logfile[128] = "fit.log";
static char *FIXED = "# FIXED";
static char *GNUFITLOG = "FIT_LOG";
static char *FITLIMIT = "FIT_LIMIT";
static char *FITSTARTLAMBDA = "FIT_START_LAMBDA";
static char *FITLAMBDAFACTOR = "FIT_LAMBDA_FACTOR";
static char *FITMAXITER = "FIT_MAXITER";	/* HBB 970304: maxiter patch */
static char *FITSCRIPT = "FIT_SCRIPT";
static char *DEFAULT_CMD = "replot";	/* if no fitscript spec. */
static char last_fit_command[LASTFITCMDLENGTH+1] = "";


static FILE *log_f = NULL;

static int num_data, num_params;
static int columns;
static double *fit_x = 0, *fit_y = 0, *fit_z = 0, *err_data = 0, *a = 0;
static TBOOLEAN ctrlc_flag = FALSE;
static TBOOLEAN user_stop = FALSE;

static struct udft_entry func;

typedef char fixstr[MAX_ID_LEN+1];

static fixstr *par_name;

static double startup_lambda = 0, lambda_down_factor = LAMBDA_DOWN_FACTOR,
 lambda_up_factor = LAMBDA_UP_FACTOR;

/*****************************************************************
			 internal Prototypes
*****************************************************************/

static RETSIGTYPE ctrlc_handle __PROTO((int an_int));
static void ctrlc_setup __PROTO((void));
static void printmatrix __PROTO((double **C, int m, int n));
static void print_matrix_and_vectors __PROTO((double **C, double *d, double *r, int m, int n));
static marq_res_t marquardt __PROTO((double a[], double **alpha, double *chisq,
				     double *lambda));
static TBOOLEAN analyze __PROTO((double a[], double **alpha, double beta[],
				 double *chisq));
static void calculate __PROTO((double *zfunc, double **dzda, double a[]));
static void call_gnuplot __PROTO((double *par, double *data));
static TBOOLEAN fit_interrupt __PROTO((void));
static TBOOLEAN regress __PROTO((double a[]));
static void show_fit __PROTO((int i, double chisq, double last_chisq, double *a,
			      double lambda, FILE * device));
static TBOOLEAN is_empty __PROTO((char *s));
static TBOOLEAN is_variable __PROTO((char *s));
static double getdvar __PROTO((char *varname));
static double createdvar __PROTO((char *varname, double value));
static void splitpath __PROTO((char *s, char *p, char *f));
static void backup_file __PROTO((char *, const char *));


/*****************************************************************
    Small function to write the last fit command into a file
    Arg: Pointer to the file; if NULL, nothing is written,
         but only the size of the string is returned.
*****************************************************************/

size_t wri_to_fil_last_fit_cmd(fp)
FILE *fp;
{
    if (fp == NULL)
	return strlen(last_fit_command);
    else
	return (size_t) fputs(last_fit_command, fp);
}


/*****************************************************************
    This is called when a SIGINT occurs during fit
*****************************************************************/

static RETSIGTYPE ctrlc_handle(an_int)
int an_int;
{
#ifdef OS2
    (void) signal(an_int, SIG_ACK);
#else
    /* reinstall signal handler (necessary on SysV) */
    (void) signal(SIGINT, (sigfunc) ctrlc_handle);
#endif
    ctrlc_flag = TRUE;
}


/*****************************************************************
    setup the ctrl_c signal handler
*****************************************************************/
static void ctrlc_setup()
{
/*
 *  MSDOS defines signal(SIGINT) but doesn't handle it through
 *  real interrupts. So there remain cases in which a ctrl-c may
 *  be uncaught by signal. We must use kbhit() instead that really
 *  serves the keyboard interrupt (or write an own interrupt func
 *  which also generates #ifdefs)
 *
 *  I hope that other OSes do it better, if not... add #ifdefs :-(
 */
#if (defined(__EMX__) || !defined(MSDOS) && !defined(DOS386)) && !defined(ATARI) && !defined(MTOS)
    (void) signal(SIGINT, (sigfunc) ctrlc_handle);
#endif
}


/*****************************************************************
    getch that handles also function keys etc.
*****************************************************************/
#if defined(MSDOS) || defined(DOS386)

/* HBB 980317: added a prototype... */
int getchx __PROTO((void));

int getchx()
{
    register int c = getch();
    if (!c || c == 0xE0) {
	c <<= 8;
	c |= getch();
    }
    return c;
}
#endif

/*****************************************************************
    in case of fatal errors
*****************************************************************/
void error_ex()
{
    char *sp;

    strncpy(fitbuf, "         ", 9);		/* start after GNUPLOT> */
    sp = strchr(fitbuf, NUL);
    while (*--sp == '\n')
	;
    strcpy(sp + 1, "\n\n");	/* terminate with exactly 2 newlines */
    fputs(fitbuf, STANDARD);
    if (log_f) {
	fprintf(log_f, "BREAK: %s", fitbuf);
	(void) fclose(log_f);
	log_f = NULL;
    }
    if (func.at) {
	free(func.at);		/* release perm. action table */
	func.at = (struct at_type *) NULL;
    }
    /* restore original SIGINT function */
#if !defined(ATARI) && !defined(MTOS)
    interrupt_setup();
#endif

    bail_to_command_line();
}


/*****************************************************************
    New utility routine: print a matrix (for debugging the alg.)
*****************************************************************/
static void printmatrix(C, m, n)
double **C;
int m, n;
{
    int i, j;

    for (i = 0; i < m; i++) {
	for (j = 0; j < n - 1; j++)
	    Dblf2("%.8g |", C[i][j]);
	Dblf2("%.8g\n", C[i][j]);
    }
    Dblf("\n");
}

/**************************************************************************
    Yet another debugging aid: print matrix, with diff. and residue vector
**************************************************************************/
static void print_matrix_and_vectors(C, d, r, m, n)
double **C;
double *d, *r;
int m, n;
{
    int i, j;

    for (i = 0; i < m; i++) {
	for (j = 0; j < n; j++)
	    Dblf2("%8g ", C[i][j]);
	Dblf3("| %8g | %8g\n", d[i], r[i]);
    }
    Dblf("\n");
}


/*****************************************************************
    Marquardt's nonlinear least squares fit
*****************************************************************/
static marq_res_t marquardt(a, C, chisq, lambda)
double a[];
double **C;
double *chisq;
double *lambda;
{
    int i, j;
    static double *da = 0,	/* delta-step of the parameter */
    *temp_a = 0,		/* temptative new params set   */
    *d = 0, *tmp_d = 0, **tmp_C = 0, *residues = 0;
    double tmp_chisq;

    /* Initialization when lambda == -1 */

    if (*lambda == -1) {	/* Get first chi-square check */
	TBOOLEAN analyze_ret;

	temp_a = vec(num_params);
	d = vec(num_data + num_params);
	tmp_d = vec(num_data + num_params);
	da = vec(num_params);
	residues = vec(num_data + num_params);
	tmp_C = matr(num_data + num_params, num_params);

	analyze_ret = analyze(a, C, d, chisq);

	/* Calculate a useful startup value for lambda, as given by Schwarz */
	/* FIXME: this is doesn't turn out to be much better, really... */
	if (startup_lambda != 0)
	    *lambda = startup_lambda;
	else {
	    *lambda = 0;
	    for (i = 0; i < num_data; i++)
		for (j = 0; j < num_params; j++)
		    *lambda += C[i][j] * C[i][j];
	    *lambda = sqrt(*lambda / num_data / num_params);
	}

	/* Fill in the lower square part of C (the diagonal is filled in on
	   each iteration, see below) */
	for (i = 0; i < num_params; i++)
	    for (j = 0; j < i; j++)
		C[num_data + i][j] = 0, C[num_data + j][i] = 0;
	/*printmatrix(C, num_data+num_params, num_params); */
	return analyze_ret ? OK : ERROR;
    }
    /* once converged, free dynamic allocated vars */

    if (*lambda == -2) {
	free(d);
	free(tmp_d);
	free(da);
	free(temp_a);
	free(residues);
	free_matr(tmp_C);
	return OK;
    }
    /* Givens calculates in-place, so make working copies of C and d */

    for (j = 0; j < num_data + num_params; j++)
	memcpy(tmp_C[j], C[j], num_params * sizeof(double));
    memcpy(tmp_d, d, num_data * sizeof(double));

    /* fill in additional parts of tmp_C, tmp_d */

    for (i = 0; i < num_params; i++) {
	/* fill in low diag. of tmp_C ... */
	tmp_C[num_data + i][i] = *lambda;
	/* ... and low part of tmp_d */
	tmp_d[num_data + i] = 0;
    }
    /* printmatrix(tmp_C, num_data+num_params, num_params); */

    /* FIXME: residues[] isn't used at all. Why? Should it be used? */

    Givens(tmp_C, tmp_d, da, residues, num_params + num_data, num_params, 1);
    /*print_matrix_and_vectors (tmp_C, tmp_d, residues,
       num_params+num_data, num_params); */

    /* check if trial did ameliorate sum of squares */

    for (j = 0; j < num_params; j++)
	temp_a[j] = a[j] + da[j];

    if (!analyze(temp_a, tmp_C, tmp_d, &tmp_chisq)) {
	/* FIXME: will never be reached: always returns TRUE */
	return ERROR;
    }

    if (tmp_chisq < *chisq) {	/* Success, accept new solution */
	if (*lambda > MIN_LAMBDA) {
	    (void) putc('/', stderr);
	    *lambda /= lambda_down_factor;
	}
	*chisq = tmp_chisq;
	for (j = 0; j < num_data; j++) {
	    memcpy(C[j], tmp_C[j], num_params * sizeof(double));
	    d[j] = tmp_d[j];
	}
	for (j = 0; j < num_params; j++)
	    a[j] = temp_a[j];
	return BETTER;
    } else {			/* failure, increase lambda and return */
	(void) putc('*', stderr);
	*lambda *= lambda_up_factor;
	return WORSE;
    }
}


/* FIXME: in the new code, this function doesn't really do enough to be
 * useful. Maybe it ought to be deleted, i.e. integrated with
 * calculate() ?
 */
/*****************************************************************
    compute chi-square and numeric derivations
*****************************************************************/
static TBOOLEAN analyze(a, C, d, chisq)
double a[];
double **C;
double d[];
double *chisq;
{
/*
 *  used by marquardt to evaluate the linearized fitting matrix C
 *  and vector d, fills in only the top part of C and d
 *  I don't use a temporary array zfunc[] any more. Just use
 *  d[] instead.
 */
    int i, j;

    *chisq = 0;
    calculate(d, C, a);

    for (i = 0; i < num_data; i++) {
	/* note: order reversed, as used by Schwarz */
	d[i] = (d[i] - fit_z[i]) / err_data[i];
	*chisq += d[i] * d[i];
	for (j = 0; j < num_params; j++)
	    C[i][j] /= err_data[i];
    }
    /* FIXME: why return a value that is always TRUE ? */
    return TRUE;
}


/* To use the more exact, but slower two-side formula, activate the
   following line: */
/*#define TWO_SIDE_DIFFERENTIATION */
/*****************************************************************
    compute function values and partial derivatives of chi-square
*****************************************************************/
static void calculate(zfunc, dzda, a)
double *zfunc;
double **dzda;
double a[];
{
    int k, p;
    double tmp_a;
    double *tmp_high, *tmp_pars;
#ifdef TWO_SIDE_DIFFERENTIATION
    double *tmp_low;
#endif

    tmp_high = vec(num_data);	/* numeric derivations */
#ifdef TWO_SIDE_DIFFERENTIATION
    tmp_low = vec(num_data);
#endif
    tmp_pars = vec(num_params);

    /* first function values */

    call_gnuplot(a, zfunc);

    /* then derivatives */

    for (p = 0; p < num_params; p++)
	tmp_pars[p] = a[p];
    for (p = 0; p < num_params; p++) {
	tmp_a = fabs(a[p]) < NEARLY_ZERO ? NEARLY_ZERO : a[p];
	tmp_pars[p] = tmp_a * (1 + DELTA);
	call_gnuplot(tmp_pars, tmp_high);
#ifdef TWO_SIDE_DIFFERENTIATION
	tmp_pars[p] = tmp_a * (1 - DELTA);
	call_gnuplot(tmp_pars, tmp_low);
#endif
	for (k = 0; k < num_data; k++)
#ifdef TWO_SIDE_DIFFERENTIATION
	    dzda[k][p] = (tmp_high[k] - tmp_low[k]) / (2 * tmp_a * DELTA);
#else
	    dzda[k][p] = (tmp_high[k] - zfunc[k]) / (tmp_a * DELTA);
#endif
	tmp_pars[p] = a[p];
    }

#ifdef TWO_SIDE_DIFFERENTIATION
    free(tmp_low);
#endif
    free(tmp_high);
    free(tmp_pars);
}


/*****************************************************************
    call internal gnuplot functions
*****************************************************************/
static void call_gnuplot(par, data)
double *par;
double *data;
{
    int i;
    struct value v;

    /* set parameters first */
    for (i = 0; i < num_params; i++) {
	(void) Gcomplex(&v, par[i], 0.0);
	setvar(par_name[i], v);
    }

    for (i = 0; i < num_data; i++) {
	/* calculate fit-function value */
	(void) Gcomplex(&func.dummy_values[0], fit_x[i], 0.0);
	(void) Gcomplex(&func.dummy_values[1], fit_y[i], 0.0);
	evaluate_at(func.at, &v);
	if (undefined)
	    Eex("Undefined value during function evaluation");
	data[i] = real(&v);
    }
}


/*****************************************************************
    handle user interrupts during fit
*****************************************************************/
static TBOOLEAN fit_interrupt()
{
    while (TRUE) {
	fputs("\n\n(S)top fit, (C)ontinue, (E)xecute FIT_SCRIPT:  ", STANDARD);
	switch (getc(stdin)) {

	case EOF:
	case 's':
	case 'S':
	    fputs("Stop.", STANDARD);
	    user_stop = TRUE;
	    return FALSE;

	case 'c':
	case 'C':
	    fputs("Continue.", STANDARD);
	    return TRUE;

	case 'e':
	case 'E':{
		int i;
		struct value v;
		char *tmp;

		tmp = (fit_script != 0 && *fit_script) ? fit_script : DEFAULT_CMD;
		fprintf(STANDARD, "executing: %s", tmp);
		/* set parameters visible to gnuplot */
		for (i = 0; i < num_params; i++) {
		    (void) Gcomplex(&v, a[i], 0.0);
		    setvar(par_name[i], v);
		}
		sprintf(input_line, tmp);
		(void) do_line();
	    }
	}
    }
    return TRUE;
}


/*****************************************************************
    frame routine for the marquardt-fit
*****************************************************************/
static TBOOLEAN regress(a)
double a[];
{
    double **covar, *dpar, **C, chisq, last_chisq, lambda;
    int iter, i, j;
    marq_res_t res;

    chisq = last_chisq = INFINITY;
    C = matr(num_data + num_params, num_params);
    lambda = -1;		/* use sign as flag */
    iter = 0;			/* iteration counter  */

    /* ctrlc now serves as Hotkey */
    ctrlc_setup();

    /* Initialize internal variables and 1st chi-square check */
    if ((res = marquardt(a, C, &chisq, &lambda)) == ERROR)
	Eex("FIT: error occured during fit");
    res = BETTER;

    show_fit(iter, chisq, chisq, a, lambda, STANDARD);
    show_fit(iter, chisq, chisq, a, lambda, log_f);

    /* MAIN FIT LOOP: do the regression iteration */

    /* HBB 981118: initialize new variable 'user_break' */
    user_stop = FALSE;

    do {
/*
 *  MSDOS defines signal(SIGINT) but doesn't handle it through
 *  real interrupts. So there remain cases in which a ctrl-c may
 *  be uncaught by signal. We must use kbhit() instead that really
 *  serves the keyboard interrupt (or write an own interrupt func
 *  which also generates #ifdefs)
 *
 *  I hope that other OSes do it better, if not... add #ifdefs :-(
 *  EMX does not have kbhit.
 * 
 *  HBB: I think this can be enabled for DJGPP V2. SIGINT is actually
 *  handled there, AFAIK.
 */
#if ((defined(MSDOS) || defined(DOS386)) && !defined(__EMX__)) || defined(ATARI) || defined(MTOS)
	if (kbhit()) {
	    do {
		getchx();
	    } while (kbhit());
	    ctrlc_flag = TRUE;
	}
#endif

	if (ctrlc_flag) {
	    show_fit(iter, chisq, last_chisq, a, lambda, STANDARD);
	    ctrlc_flag = FALSE;
	    if (!fit_interrupt())	/* handle keys */
		break;
	}
	if (res == BETTER) {
	    iter++;
	    last_chisq = chisq;
	}
	if ((res = marquardt(a, C, &chisq, &lambda)) == BETTER)
	    show_fit(iter, chisq, last_chisq, a, lambda, STANDARD);
    } while ((res != ERROR)
	     && (lambda < MAX_LAMBDA)
	     && ((maxiter == 0) || (iter <= maxiter))
	     && (res == WORSE
		 || ((chisq > NEARLY_ZERO)
		     ? ((last_chisq - chisq) / chisq)
		     : (last_chisq - chisq)) > epsilon
	     )
	);

    /* fit done */

#if !defined(ATARI) && !defined(MTOS)
    /* restore original SIGINT function */
    interrupt_setup();
#endif

    /* HBB 970304: the maxiter patch: */
    if ((maxiter > 0) && (iter > maxiter)) {
	Dblf2("\nMaximum iteration count (%d) reached. Fit stopped.\n", maxiter);
    } else if (user_stop) {
	Dblf2("\nThe fit was stopped by the user after %d iterations.\n", iter);
    } else {
	Dblf2("\nAfter %d iterations the fit converged.\n", iter);
    }

    Dblf2("final sum of squares of residuals : %g\n", chisq);
    if (chisq > NEARLY_ZERO) {
	Dblf2("rel. change during last iteration : %g\n\n", (chisq - last_chisq) / chisq);
    } else {
	Dblf2("abs. change during last iteration : %g\n\n", (chisq - last_chisq));
    }

    if (res == ERROR)
	Eex("FIT: error occured during fit");

    /* compute errors in the parameters */

    if (num_data == num_params) {
	int i;

	Dblf("\nExactly as many data points as there are parameters.\n");
	Dblf("In this degenerate case, all errors are zero by definition.\n\n");
	Dblf("Final set of parameters \n");
	Dblf("======================= \n\n");
	for (i = 0; i < num_params; i++)
	    Dblf3("%-15.15s = %-15g\n", par_name[i], a[i]);
    } else if (chisq < NEARLY_ZERO) {
	int i;

	Dblf("\nHmmmm.... Sum of squared residuals is zero. Can't compute errors.\n\n");
	Dblf("Final set of parameters \n");
	Dblf("======================= \n\n");
	for (i = 0; i < num_params; i++)
	    Dblf3("%-15.15s = %-15g\n", par_name[i], a[i]);
    } else {
	Dblf2("degrees of freedom (ndf) : %d\n",  num_data - num_params);
	Dblf2("rms of residuals      (stdfit) = sqrt(WSSR/ndf)      : %g\n", sqrt(chisq / (num_data - num_params)));
 	Dblf2("variance of residuals (reduced chisquare) = WSSR/ndf : %g\n\n", chisq / (num_data - num_params));
 
	/* get covariance-, Korrelations- and Kurvature-Matrix */
	/* and errors in the parameters                     */

	/* compute covar[][] directly from C */
	Givens(C, 0, 0, 0, num_data, num_params, 0);
	/*printmatrix(C, num_params, num_params); */

	/* Use lower square of C for covar */
	covar = C + num_data;
	Invert_RtR(C, covar, num_params);
	/*printmatrix(covar, num_params, num_params); */

	/* calculate unscaled parameter errors in dpar[]: */
	dpar = vec(num_params);
	for (i = 0; i < num_params; i++) {
	    /* FIXME: can this still happen ? */
	    if (covar[i][i] <= 0.0)	/* HBB: prevent floating point exception later on */
		Eex("Calculation error: non-positive diagonal element in covar. matrix");
	    dpar[i] = sqrt(covar[i][i]);
	}

	/* transform covariances into correlations */
	for (i = 0; i < num_params; i++) {
	    /* only lower triangle needs to be handled */
	    for (j = 0; j <= i; j++)
		covar[i][j] /= dpar[i] * dpar[j];
	}

	/* scale parameter errors based on chisq */
	chisq = sqrt(chisq / (num_data - num_params));
	for (i = 0; i < num_params; i++)
	    dpar[i] *= chisq;

	Dblf("Final set of parameters            Asymptotic Standard Error\n");
	Dblf("=======================            ==========================\n\n");

	for (i = 0; i < num_params; i++) {
	    double temp =
	    (fabs(a[i]) < NEARLY_ZERO) ? 0.0 : fabs(100.0 * dpar[i] / a[i]);
	    Dblf6("%-15.15s = %-15g  %-3.3s %-12.4g (%.4g%%)\n",
		  par_name[i], a[i], PLUSMINUS, dpar[i], temp);
	}

	Dblf("\n\ncorrelation matrix of the fit parameters:\n\n");
	Dblf("               ");

	for (j = 0; j < num_params; j++)
	    Dblf2("%-6.6s ", par_name[j]);

	Dblf("\n");
	for (i = 0; i < num_params; i++) {
	    Dblf2("%-15.15s", par_name[i]);
	    for (j = 0; j <= i; j++) {
		/* Only print lower triangle of symmetric matrix */
		Dblf2("%6.3f ", covar[i][j]);
	    }
	    Dblf("\n");
	}

	free(dpar);
    }

    /* HBB 990220: re-imported this snippet from older versions. Finally,
     * some user noticed that it *is* necessary, after all. Not even
     * Carsten Grammes himself remembered what it was for... :-(
     * The thing is: the value of the last parameter is not reset to
     * its original one after the derivatives have been calculated
     */
    /* restore last parameter's value (not done by calculate) */
    {
	struct value val;
	Gcomplex (&val, a[num_params-1], 0.0);
	setvar (par_name[num_params-1], val);
     }

    /* call destructor for allocated vars */
    lambda = -2;		/* flag value, meaning 'destruct!' */
    (void) marquardt(a, C, &chisq, &lambda);

    free_matr(C);
    return TRUE;
}


/*****************************************************************
    display actual state of the fit
*****************************************************************/
static void show_fit(i, chisq, last_chisq, a, lambda, device)
int i;
double chisq;
double last_chisq;
double *a;
double lambda;
FILE *device;
{
    int k;

    fprintf(device, "\n\n\
Iteration %d\n\
WSSR        : %-15g   delta(WSSR)/WSSR   : %g\n\
delta(WSSR) : %-15g   limit for stopping : %g\n\
lambda	  : %g\n\n%s parameter values\n\n",
      i, chisq, chisq > NEARLY_ZERO ? (chisq - last_chisq) / chisq : 0.0,
	    chisq - last_chisq, epsilon, lambda,
	    (i > 0 ? "resultant" : "initial set of free"));
    for (k = 0; k < num_params; k++)
	fprintf(device, "%-15.15s = %g\n", par_name[k], a[k]);
}



/*****************************************************************
    is_empty: check for valid string entries
*****************************************************************/
static TBOOLEAN is_empty(s)
char *s;
{
    while (*s == ' ' || *s == '\t' || *s == '\n')
	s++;
    return (TBOOLEAN) (*s == '#' || *s == '\0');
}


/*****************************************************************
    get next word of a multi-word string, advance pointer
*****************************************************************/
char *get_next_word(s, subst)
char **s;
char *subst;
{
    char *tmp = *s;

    while (*tmp == ' ' || *tmp == '\t' || *tmp == '=')
	tmp++;
    if (*tmp == '\n' || *tmp == '\0')	/* not found */
	return NULL;
    if ((*s = strpbrk(tmp, " =\t\n")) == NULL)
	*s = tmp + strlen(tmp);
    *subst = **s;
    *(*s)++ = '\0';
    return tmp;
}


/*****************************************************************
    check for variable identifiers
*****************************************************************/
static TBOOLEAN is_variable(s)
char *s;
{
    while (*s != '\0') {
	if (!isalnum((int) *s) && *s != '_')
	    return FALSE;
	s++;
    }
    return TRUE;
}

/*****************************************************************
    first time settings
*****************************************************************/
void init_fit()
{
    func.at = (struct at_type *) NULL;	/* need to parse 1 time */
}


/*****************************************************************
	    Set a GNUPLOT user-defined variable
******************************************************************/

void setvar(varname, data)
char *varname;
struct value data;
{
    register struct udvt_entry *udv_ptr = first_udv, *last = first_udv;

    /* check if it's already in the table... */

    while (udv_ptr) {
	last = udv_ptr;
	if (!strcmp(varname, udv_ptr->udv_name))
	    break;
	udv_ptr = udv_ptr->next_udv;
    }

    if (!udv_ptr) {		/* generate new entry */
	last->next_udv = udv_ptr = (struct udvt_entry *)
	    gp_alloc(sizeof(struct udvt_entry), "fit setvar");
	udv_ptr->next_udv = NULL;
    }
    safe_strncpy(udv_ptr->udv_name, varname, sizeof(udv_ptr->udv_name));
    udv_ptr->udv_value = data;
    udv_ptr->udv_undef = FALSE;
}



/*****************************************************************
    Read INTGR Variable value, return 0 if undefined or wrong type
*****************************************************************/
int getivar(varname)
char *varname;
{
    register struct udvt_entry *udv_ptr = first_udv;

    while (udv_ptr) {
	if (!strcmp(varname, udv_ptr->udv_name))
	    return udv_ptr->udv_value.type == INTGR
		? udv_ptr->udv_value.v.int_val	/* valid */
		: 0;		/* wrong type */
	udv_ptr = udv_ptr->next_udv;
    }
    return 0;			/* not in table */
}


/*****************************************************************
    Read DOUBLE Variable value, return 0 if undefined or wrong type
   I dont think it's a problem that it's an integer - div
*****************************************************************/
static double getdvar(varname)
char *varname;
{
    register struct udvt_entry *udv_ptr = first_udv;

    for (; udv_ptr; udv_ptr = udv_ptr->next_udv)
	if (strcmp(varname, udv_ptr->udv_name) == 0)
	    return real(&(udv_ptr->udv_value));

    /* get here => not found */
    return 0;
}

/*****************************************************************
   like getdvar, but
   - convert it from integer to real if necessary
   - create it with value INITIAL_VALUE if not found or undefined
*****************************************************************/
static double createdvar(varname, value)
char *varname;
double value;
{
    register struct udvt_entry *udv_ptr = first_udv;

    for (; udv_ptr; udv_ptr = udv_ptr->next_udv)
	if (strcmp(varname, udv_ptr->udv_name) == 0) {
	    if (udv_ptr->udv_undef) {
		udv_ptr->udv_undef = 0;
		(void) Gcomplex(&udv_ptr->udv_value, value, 0.0);
	    } else if (udv_ptr->udv_value.type == INTGR) {
		(void) Gcomplex(&udv_ptr->udv_value, (double) udv_ptr->udv_value.v.int_val, 0.0);
	    }
	    return real(&(udv_ptr->udv_value));
	}
    /* get here => not found */

    {
	struct value tempval;
	(void) Gcomplex(&tempval, value, 0.0);
	setvar(varname, tempval);
    }

    return value;
}


/*****************************************************************
    Split Identifier into path and filename
*****************************************************************/
static void splitpath(s, p, f)
char *s;
char *p;
char *f;
{
    register char *tmp;
    tmp = s + strlen(s) - 1;
    while (*tmp != '\\' && *tmp != '/' && *tmp != ':' && tmp - s >= 0)
	tmp--;
    strcpy(f, tmp + 1);
    safe_strncpy(p, s, (size_t) (tmp - s + 1));
    p[tmp - s + 1] = NUL;
}


/*****************************************************************
    write the actual parameters to start parameter file
*****************************************************************/
void update(pfile, npfile)
char *pfile, *npfile;
{
    char fnam[256], path[256], sstr[256], pname[64], tail[127], *s = sstr,
    *tmp, c;
    char ifilename[256], *ofilename;
    FILE *of, *nf;
    double pval;


    /* update pfile npfile:
       if npfile is a valid file name,
       take pfile as input file and
       npfile as output file
     */
    if (VALID_FILENAME(npfile)) {
	safe_strncpy(ifilename, pfile, sizeof(ifilename));
	ofilename = npfile;
    } else {
#ifdef BACKUP_FILESYSTEM
	/* filesystem will keep original as previous version */
	safe_strncpy(ifilename, pfile, sizeof(ifilename));
#else
	backup_file(ifilename, pfile);	/* will Eex if it fails */
#endif
	ofilename = pfile;
    }

    /* split into path and filename */
    splitpath(ifilename, path, fnam);
    if (!(of = fopen(ifilename, "r")))
	Eex2("parameter file %s could not be read", ifilename);

    if (!(nf = fopen(ofilename, "w")))
	Eex2("new parameter file %s could not be created", ofilename);

    while (fgets(s = sstr, sizeof(sstr), of) != NULL) {

	if (is_empty(s)) {
	    fputs(s, nf);	/* preserve comments */
	    continue;
	}
	if ((tmp = strchr(s, '#')) != NULL) {
	    safe_strncpy(tail, tmp, sizeof(tail));
	    *tmp = NUL;
	} else
	    strcpy(tail, "\n");

	tmp = get_next_word(&s, &c);
	if (!is_variable(tmp) || strlen(tmp) > MAX_ID_LEN) {
	    (void) fclose(nf);
	    (void) fclose(of);
	    Eex2("syntax error in parameter file %s", fnam);
	}
	safe_strncpy(pname, tmp, sizeof(pname));
	/* next must be '=' */
	if (c != '=') {
	    tmp = strchr(s, '=');
	    if (tmp == NULL) {
		(void) fclose(nf);
		(void) fclose(of);
		Eex2("syntax error in parameter file %s", fnam);
	    }
	    s = tmp + 1;
	}
	tmp = get_next_word(&s, &c);
	if (!sscanf(tmp, "%lf", &pval)) {
	    (void) fclose(nf);
	    (void) fclose(of);
	    Eex2("syntax error in parameter file %s", fnam);
	}
	if ((tmp = get_next_word(&s, &c)) != NULL) {
	    (void) fclose(nf);
	    (void) fclose(of);
	    Eex2("syntax error in parameter file %s", fnam);
	}
	/* now modify */

	if ((pval = getdvar(pname)) == 0)
	    pval = (double) getivar(pname);

	sprintf(sstr, "%g", pval);
	if (!strchr(sstr, '.') && !strchr(sstr, 'e'))
	    strcat(sstr, ".0");	/* assure CMPLX-type */

	fprintf(nf, "%-15.15s = %-15.15s   %s", pname, sstr, tail);
    }

    if (fclose(nf) || fclose(of))
	Eex("I/O error during update");

}


/*****************************************************************
    Backup a file by renaming it to something useful. Return
    the new name in tofile
*****************************************************************/
static void backup_file(tofile, fromfile)
char *tofile;
const char *fromfile;
/* tofile must point to a char array[] or allocated data. See update() */
{
#if defined (WIN32) || defined(MSDOS) || defined(VMS)
    char *tmpn;
#endif

    /* win32 needs to have two attempts at the rename, since it may
     * be running on win32s with msdos 8.3 names
     */

/* first attempt, for all o/s other than MSDOS */

#ifndef MSDOS

    strcpy(tofile, fromfile);

#ifdef VMS
    /* replace all dots with _, since we will be adding the only
     * dot allowed in VMS names
     */
    while ((tmpn = strchr(tofile, '.')) != NULL)
	*tmpn = '_';
#endif /*VMS */

    strcat(tofile, BACKUP_SUFFIX);

    if (rename(fromfile, tofile) == 0)
	return;			/* hurrah */
#endif


#if defined (WIN32) || defined(MSDOS)

    /* first attempt for msdos. Second attempt for win32s */

    /* beware : strncpy is very dangerous since it does not guarantee
     * to terminate the string. Copy up to 8 characters. If exactly
     * chars were copied, the string is not terminated. If the
     * source string was shorter than 8 chars, no harm is done
     * (here) by writing to offset 8.
     */
    safe_strncpy(tofile, fromfile, 8);
    /* tofile[8] = NUL; */

    while ((tmpn = strchr(tofile, '.')) != NULL)
	*tmpn = '_';

    strcat(tofile, BACKUP_SUFFIX);

    if (rename(fromfile, tofile) == 0)
	return;			/* success */

#endif /* win32 || msdos */

    /* get here => rename failed. */
    Eex3("Could not rename file %s to %s", fromfile, tofile);
}


/*****************************************************************
    Interface to the classic gnuplot-software
*****************************************************************/

void do_fit()
{
    TBOOLEAN autorange_x = 3, autorange_y = 3;	/* yes */
    /* HBB 980401: new: z range specification */
    TBOOLEAN autorange_z = 3;
    double min_x, max_x;	/* range to fit */
    double min_y, max_y;	/* range to fit */
    /* HBB 980401: new: z range specification */
    double min_z, max_z;	/* range to fit */
    int dummy_x = -1, dummy_y = -1;	/* eg  fit [u=...] [v=...] */
    /* HBB 981210: memorize position of possible third [ : ] spec: */
    int zrange_token = -1;

    int i;
    double v[4];
    double tmpd;
    time_t timer;
    int token1, token2, token3;
    char *tmp;

    /* first look for a restricted x fit range... */

    if (equals(c_token, "[")) {
	c_token++;
	if (isletter(c_token)) {
	    if (equals(c_token + 1, "=")) {
		dummy_x = c_token;
		c_token += 2;
	    }
	    /* else parse it as a xmin expression */
	}
	autorange_x = load_range(FIRST_X_AXIS, &min_x, &max_x, autorange_x);
	if (!equals(c_token, "]"))
	    int_error("']' expected", c_token);
	c_token++;
    }
    /* ... and y */

    if (equals(c_token, "[")) {
	c_token++;
	if (isletter(c_token)) {
	    if (equals(c_token + 1, "=")) {
		dummy_y = c_token;
		c_token += 2;
	    }
	    /* else parse it as a ymin expression */
	}
	autorange_y = load_range(FIRST_Y_AXIS, &min_y, &max_y, autorange_y);
	if (!equals(c_token, "]"))
	    int_error("']' expected", c_token);
	c_token++;
    }
    /* HBB 980401: new: allow restricting the z range as well */
    /* ... and z */

    if (equals(c_token, "[")) {
	zrange_token = c_token++;
	if (isletter(c_token))
	    /* do *not* allow the z range being given with a variable name */
	    int_error("Can't re-name dependent variable", c_token);
	autorange_z = load_range(FIRST_Z_AXIS, &min_z, &max_z, autorange_z);
	if (!equals(c_token, "]"))
	    int_error("']' expected", c_token);
	c_token++;
#if 0 /* HBB 981210: move this to a later point */
    } else {
	/* Just in case I muck up things below: make sure that the z
	 * range is the same as the y range, if it didn't get specified
	 */
	autorange_z = autorange_y;
	min_z = min_y;
	max_z = max_y;
#endif
    }


    /* now compile the function */

    token1 = c_token;

    if (func.at) {
	free(func.at);
	func.at = NULL;		/* in case perm_at() does int_error */
    }
    dummy_func = &func;


    /* set the dummy variable names */

    if (dummy_x >= 0)
	copy_str(c_dummy_var[0], dummy_x, MAX_ID_LEN);
    else
	strcpy(c_dummy_var[0], dummy_var[0]);

    if (dummy_y >= 0)
	copy_str(c_dummy_var[0], dummy_y, MAX_ID_LEN);
    else
	strcpy(c_dummy_var[1], dummy_var[1]);

    func.at = perm_at();
    dummy_func = NULL;

    token2 = c_token;

    /* use datafile module to parse the datafile and qualifiers */

    columns = df_open(4);	/* up to 4 using specs allowed */
    if (columns == 1)
	int_error("Need 2 to 4 using specs", c_token);

    /* The following patch was made by Remko Scharroo, 25-Mar-1999
     * We need to check if one of the columns is time data, like
     * in plot2d and plot3d */

    if (datatype[FIRST_X_AXIS] == TIME) {
	if (columns < 2)
	    int_error("Need full using spec for x time data", c_token);
	df_timecol[0] = 1;
    }
    if (datatype[FIRST_Y_AXIS] == TIME) {
	if (columns < 1)
	    int_error("Need using spec for y time data", c_token);
	df_timecol[1] = 1;
    }
    /* HBB 990326: added this check. Just in case some wants to fit
     * time/date data depending on two other variables ... */
    if (datatype[FIRST_Z_AXIS] == TIME) {
	if (columns < 4)
	    int_error("Need full using spec for z time data", c_token);
	else
	    df_timecol[2] = 1;
    }
    /* End of patch by Remko Scharroo */

    /* HBB 980401: if this is a single-variable fit, we shouldn't have
     * allowed a variable name specifier for 'y': */
    if ((dummy_y >= 0) && (columns < 4))
	int_error("Can't re-name 'y' in a one-variable fit", dummy_y);

    /* HBB 981210: two range specs mean different things, depending
     * on wether this is a 2D or 3D fit */
    if (columns < 4) {
	if (zrange_token != -1)
	    int_error("Three range-specs not allowed in on-variable fit", zrange_token);
	else {
	    /* 2D fit, 2 ranges: second range is for *z*, not y: */
	    autorange_z = autorange_y;
	    if (autorange_y & 1)
		min_z = min_y;
	    if (autorange_y & 2)
		max_z = max_y;
	}
    }

    /* defer actually reading the data until we have parsed the rest
     * of the line */

    token3 = c_token;

    tmpd = getdvar(FITLIMIT);	/* get epsilon if given explicitly */
    if (tmpd < 1.0 && tmpd > 0.0)
	epsilon = tmpd;

    /* HBB 970304: maxiter patch */
    maxiter = getivar(FITMAXITER);

    /* get startup value for lambda, if given */
    tmpd = getdvar(FITSTARTLAMBDA);

    if (tmpd > 0.0) {
	startup_lambda = tmpd;
	printf("Lambda Start value set: %g\n", startup_lambda);
    }

    /* get lambda up/down factor, if given */
    tmpd = getdvar(FITLAMBDAFACTOR);

    if (tmpd > 0.0) {
	lambda_up_factor = lambda_down_factor = tmpd;
	printf("Lambda scaling factors reset:  %g\n", lambda_up_factor);
    }
    *fit_script = NUL;
    if ((tmp = getenv(FITSCRIPT)) != NULL)
	strcpy(fit_script, tmp);

    tmp = getenv(GNUFITLOG);	/* open logfile */
    if (tmp != NULL) {
	char *tmp2 = &tmp[strlen(tmp) - 1];
	if (*tmp2 == '/' || *tmp2 == '\\')
	    sprintf(logfile, "%s%s", tmp, logfile);
	else
	    strcpy(logfile, tmp);
    }
    if (!log_f && /* div */ !(log_f = fopen(logfile, "a")))
	Eex2("could not open log-file %s", logfile);
    fputs("\n\n*******************************************************************************\n", log_f);
    (void) time(&timer);
    fprintf(log_f, "%s\n\n", ctime(&timer));
    {
	char *line = NULL;

	m_capture(&line, token2, token3 - 1);
	fprintf(log_f, "FIT:    data read from %s\n", line);
	free(line);
    }

    max_data = MAX_DATA;
    fit_x = vec(max_data);	/* start with max. value */
    fit_y = vec(max_data);
    fit_z = vec(max_data);

    /* first read in experimental data */

    err_data = vec(max_data);
    num_data = 0;

    while ((i = df_readline(v, 4)) != EOF) {
	if (num_data >= max_data) {
	    /* increase max_data by factor of 1.5 */
	    max_data = (max_data * 3) / 2;
	    if (0
		|| !redim_vec(&fit_x, max_data)
		|| !redim_vec(&fit_y, max_data)
		|| !redim_vec(&fit_z, max_data)
		|| !redim_vec(&err_data, max_data)
		) {
		/* Some of the reallocations went bad: */
		df_close();
		Eex2("Out of memory in fit: too many datapoints (%d)?", max_data);
	    } else {
		/* Just so we know that the routine is at work: */
		fprintf(STANDARD, "Max. number of data points scaled up to: %d\n",
			max_data);
	    }
	}
	switch (i) {
	case DF_UNDEFINED:
	case DF_FIRST_BLANK:
	case DF_SECOND_BLANK:
	    continue;
	case 0:
	    Eex2("bad data on line %d of datafile", df_line_number);
	    break;
	case 1:		/* only z provided */
	    v[2] = v[0];
	    v[0] = (double) df_datum;
	    break;
	case 2:		/* x and z */
	    v[2] = v[1];
	    break;

	    /* only if the explicitly asked for 4 columns do we
	     * do a 3d fit. (We can get here if they didn't
	     * specify a using spec, and the file has 4 columns
	     */
	case 4:		/* x, y, z, error */
	    if (columns == 4)
		break;
	    /* else fall through */
	case 3:		/* x, z, error */
	    v[3] = v[2];	/* error */
	    v[2] = v[1];	/* z */
	    break;

	}

	/* skip this point if it is out of range */
	if (!(autorange_x & 1) && (v[0] < min_x))
	    continue;
	if (!(autorange_x & 2) && (v[0] > max_x))
	    continue;
	/* HBB 980401: yrange is only relevant for 3d-fits! */
	if (columns == 4) {
	    if (!(autorange_y & 1) && (v[1] < min_y))
		continue;
	    if (!(autorange_y & 2) && (v[1] > max_y))
		continue;
	}
	/* HBB 980401: check *z* range for all fits */
	if (!(autorange_z & 1) && (v[2] < min_z))
	    continue;
	if (!(autorange_z & 2) && (v[2] > max_z))
	    continue;

	fit_x[num_data] = v[0];
	fit_y[num_data] = v[1];
	fit_z[num_data] = v[2];

	/* we only use error if _explicitly_ asked for by a
	 * using spec
	 */
	err_data[num_data++] = (columns > 2) ? v[3] : 1;
    }
    df_close();

    if (num_data <= 1)
	Eex("No data to fit ");

    /* now resize fields to actual length: */
    redim_vec(&fit_x, num_data);
    redim_vec(&fit_y, num_data);
    redim_vec(&fit_z, num_data);
    redim_vec(&err_data, num_data);

    fprintf(log_f, "        #datapoints = %d\n", num_data);

    if (columns < 3)
	fputs("        residuals are weighted equally (unit weight)\n\n", log_f);

    {
	char *line = NULL;

	m_capture(&line, token1, token2 - 1);
	fprintf(log_f, "function used for fitting: %s\n", line);
	free(line);
    }

    /* read in parameters */

    max_params = MAX_PARAMS;	/* HBB 971023: make this resizeable */

    if (!equals(c_token, "via"))
	int_error("Need via and either parameter list or file", c_token);

    a = vec(max_params);
    par_name = (fixstr *) gp_alloc((max_params + 1) * sizeof(fixstr), "fit param");
    num_params = 0;

    if (isstring(++c_token)) {	/* It's a parameter *file* */
	TBOOLEAN fixed;
	double tmp_par;
	char c, *s;
	char sstr[MAX_LINE_LEN+1];
	FILE *f;

	quote_str(sstr, c_token++, MAX_LINE_LEN);

	/* get parameters and values out of file and ignore fixed ones */

	fprintf(log_f, "fitted parameters and initial values from file: %s\n\n", sstr);
	if (!(f = fopen(sstr, "r")))
	    Eex2("could not read parameter-file %s", sstr);
	while (TRUE) {
	    if (!fgets(s = sstr, (int) sizeof(sstr), f))	/* EOF found */
		break;
	    if ((tmp = strstr(s, FIXED)) != NULL) {	/* ignore fixed params */
		*tmp = NUL;
		fprintf(log_f, "FIXED:  %s\n", s);
		fixed = TRUE;
	    } else
		fixed = FALSE;
	    if ((tmp = strchr(s, '#')) != NULL)
		*tmp = NUL;
	    if (is_empty(s))
		continue;
	    tmp = get_next_word(&s, &c);
	    if (!is_variable(tmp) || strlen(tmp) > MAX_ID_LEN) {
		(void) fclose(f);
		Eex("syntax error in parameter file");
	    }
	    safe_strncpy(par_name[num_params], tmp, sizeof(fixstr));
	    /* next must be '=' */
	    if (c != '=') {
		tmp = strchr(s, '=');
		if (tmp == NULL) {
		    (void) fclose(f);
		    Eex("syntax error in parameter file");
		}
		s = tmp + 1;
	    }
	    tmp = get_next_word(&s, &c);
	    if (sscanf(tmp, "%lf", &tmp_par) != 1) {
		(void) fclose(f);
		Eex("syntax error in parameter file");
	    }
	    /* make fixed params visible to GNUPLOT */
	    if (fixed) {
		struct value tempval;
		(void) Gcomplex(&tempval, tmp_par, 0.0);
		/* use parname as temp */
		setvar(par_name[num_params], tempval);
	    } else {
		if (num_params >= max_params) {
		    max_params = (max_params * 3) / 2;
		    if (0
			|| !redim_vec(&a, max_params)
			|| !(par_name = gp_realloc(par_name, (max_params + 1) * sizeof(fixstr), "fit param resize"))
			) {
			(void) fclose(f);
			Eex("Out of memory in fit: too many parameters?");
		    }
		}
		a[num_params++] = tmp_par;
	    }

	    if ((tmp = get_next_word(&s, &c)) != NULL) {
		(void) fclose(f);
		Eex("syntax error in parameter file");
	    }
	}
	(void) fclose(f);

    } else {
	/* not a string after via: it's a variable listing */

	fputs("fitted parameters initialized with current variable values\n\n", log_f);
	do {
	    if (!isletter(c_token))
		Eex("no parameter specified");
	    capture(par_name[num_params], c_token, c_token, (int) sizeof(par_name[0]));
	    if (num_params >= max_params) {
		max_params = (max_params * 3) / 2;
		if (0
		    || !redim_vec(&a, max_params)
		    || !(par_name = gp_realloc(par_name, (max_params + 1) * sizeof(fixstr), "fit param resize"))
		    ) {
		    Eex("Out of memory in fit: too many parameters?");
		}
	    }
	    /* create variable if it doesn't exist */
	    a[num_params] = createdvar(par_name[num_params], INITIAL_VALUE);
	    ++num_params;
	} while (equals(++c_token, ",") && ++c_token);
    }

    redim_vec(&a, num_params);
    par_name = (fixstr *) gp_realloc(par_name, (num_params + 1) * sizeof(fixstr), "fit param");

    if (num_data < num_params)
	Eex("Number of data points smaller than number of parameters");

    /* avoid parameters being equal to zero */
    for (i = 0; i < num_params; i++)
	if (a[i] == 0)
	    a[i] = NEARLY_ZERO;

    (void) regress(a);

    (void) fclose(log_f);
    log_f = NULL;
    free(fit_x);
    free(fit_y);
    free(fit_z);
    free(err_data);
    free(a);
    free(par_name);
    if (func.at) {
	free(func.at);		/* release perm. action table */
	func.at = (struct at_type *) NULL;
    }
    safe_strncpy(last_fit_command, input_line, sizeof(last_fit_command));
}

#if defined(ATARI) || defined(MTOS)
static int kbhit()
{
    fd_set rfds;
    struct timeval timeout;

    timeout.tv_sec = 0;
    timeout.tv_usec = 0;
    rfds = (fd_set) (1L << fileno(stdin));
    return ((select(0, &rfds, NULL, NULL, &timeout) > 0) ? 1 : 0);
}
#endif