| Revision: | 2.4 |
| Committed: | Tue Feb 25 02:47:21 2003 UTC (22 years, 2 months ago) by greg |
| Content type: | text/plain |
| Branch: | MAIN |
| CVS Tags: | rad5R4, rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R5, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1, rad5R3, HEAD |
| Changes since 2.3: | +1 -56 lines |
| Log Message: | Replaced inline copyright notice with #include "copyright.h" |
| # | Content |
|---|---|
| 1 | #ifndef lint |
| 2 | static const char RCSid[] = "$Id$"; |
| 3 | #endif |
| 4 | /* |
| 5 | * Basic linear regression calculation. |
| 6 | */ |
| 7 | |
| 8 | #include "copyright.h" |
| 9 | |
| 10 | #include <math.h> |
| 11 | |
| 12 | #include "linregr.h" |
| 13 | |
| 14 | |
| 15 | void |
| 16 | lrclear(l) /* initialize sum */ |
| 17 | register LRSUM *l; |
| 18 | { |
| 19 | l->xs = l->ys = l->xxs = l->yys = l->xys = 0.0; |
| 20 | l->n = 0; |
| 21 | } |
| 22 | |
| 23 | |
| 24 | int |
| 25 | flrpoint(x, y, l) /* add point (x,y) to sum */ |
| 26 | double x, y; |
| 27 | register LRSUM *l; |
| 28 | { |
| 29 | l->xs += x; |
| 30 | l->ys += y; |
| 31 | l->xxs += x*x; |
| 32 | l->yys += y*y; |
| 33 | l->xys += x*y; |
| 34 | return(++l->n); |
| 35 | } |
| 36 | |
| 37 | |
| 38 | int |
| 39 | lrfit(r, l) /* compute linear regression */ |
| 40 | register LRLIN *r; |
| 41 | register LRSUM *l; |
| 42 | { |
| 43 | double nxvar, nyvar; |
| 44 | |
| 45 | if (l->n < 2) |
| 46 | return(-1); |
| 47 | nxvar = l->xxs - l->xs*l->xs/l->n; |
| 48 | nyvar = l->yys - l->ys*l->ys/l->n; |
| 49 | if (nxvar == 0.0 || nyvar == 0.0) |
| 50 | return(-1); |
| 51 | r->slope = (l->xys - l->xs*l->ys/l->n) / nxvar; |
| 52 | r->intercept = (l->ys - r->slope*l->xs) / l->n; |
| 53 | r->correlation = r->slope*sqrt(nxvar/nyvar); |
| 54 | return(0); |
| 55 | } |