src/common/linregr.c

/* Copyright (c) 1991 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Basic linear regression calculation.
 */

#include "linregr.h"


lrclear(l)                      /* initialize sum */
register LRSUM  *l;
{
        l->xs = l->ys = l->xxs = l->yys = l->xys = 0.0;
        l->n = 0;
}


flrpoint(x, y, l)               /* add point (x,y) to sum */
double  x, y;
register LRSUM  *l;
{
        l->xs += x;
        l->ys += y;
        l->xxs += x*x;
        l->yys += y*y;
        l->xys += x*y;
        return(++l->n);
}


lrfit(r, l)                     /* compute linear regression */
register LRLIN  *r;
register LRSUM  *l;
{
        double  nxvar, nyvar;

        if (l->n < 2)
                return(-1);
        nxvar = l->xxs - l->xs*l->xs/l->n;
        nyvar = l->yys - l->ys*l->ys/l->n;
        if (nxvar == 0.0 || nyvar == 0.0)
                return(-1);
        r->slope = (l->xys - l->xs*l->ys/l->n) / nxvar;
        r->intercept = (l->ys - r->slope*l->xs) / l->n;
        r->correlation = r->slope*sqrt(nxvar/nyvar);
        return(0);
}
Revision:	2.1
Committed:	Tue Nov 12 16:55:46 1991 UTC (33 years, 11 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.1:	+0 -0 lines
Log Message:	updated revision number for release 2.0
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1991 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Basic linear regression calculation.
9			*/
10
11			#include "linregr.h"
12
13
14			lrclear(l) /* initialize sum */
15			register LRSUM *l;
16			{
17			l->xs = l->ys = l->xxs = l->yys = l->xys = 0.0;
18			l->n = 0;
19			}
20
21
22			flrpoint(x, y, l) /* add point (x,y) to sum */
23			double x, y;
24			register LRSUM *l;
25			{
26			l->xs += x;
27			l->ys += y;
28			l->xxs += x*x;
29			l->yys += y*y;
30			l->xys += x*y;
31			return(++l->n);
32			}
33
34
35			lrfit(r, l) /* compute linear regression */
36			register LRLIN *r;
37			register LRSUM *l;
38			{
39			double nxvar, nyvar;
40
41			if (l->n < 2)
42			return(-1);
43			nxvar = l->xxs - l->xs*l->xs/l->n;
44			nyvar = l->yys - l->ys*l->ys/l->n;
45			if (nxvar == 0.0 \|\| nyvar == 0.0)
46			return(-1);
47			r->slope = (l->xys - l->xs*l->ys/l->n) / nxvar;
48			r->intercept = (l->ys - r->slope*l->xs) / l->n;
49			r->correlation = r->slope*sqrt(nxvar/nyvar);
50			return(0);
51			}