| 1 | #include "slalib.h"
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| 2 | #include "slamac.h"
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| 3 | void slaPxy ( int np, double xye[][2], double xym[][2],
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| 4 | double coeffs[6], double xyp[][2],
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| 5 | double *xrms, double *yrms, double *rrms )
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| 6 | /*
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| 7 | ** - - - - - - -
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| 8 | ** s l a P x y
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| 9 | ** - - - - - - -
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| 10 | **
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| 11 | ** Given arrays of "expected" and "measured" [x,y] coordinates, and a
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| 12 | ** linear model relating them (as produced by slaFitxy), compute
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| 13 | ** the array of "predicted" coordinates and the rms residuals.
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| 14 | **
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| 15 | ** Given:
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| 16 | ** np int number of samples
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| 17 | ** xye double[np] expected [x,y] for each sample
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| 18 | ** xym double[np] measured [x,y] for each sample
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| 19 | ** coeffs double[6] coefficients of model (see below)
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| 20 | **
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| 21 | ** Returned:
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| 22 | ** xyp double[np] predicted [x,y] for each sample
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| 23 | ** *xrms double RMS in x
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| 24 | ** *yrms double RMS in y
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| 25 | ** *rrms double total RMS (vector sum of xrms and yrms)
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| 26 | **
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| 27 | ** The model is supplied in the array coeffs. Naming the
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| 28 | ** elements of coeff as follows:
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| 29 | **
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| 30 | ** coeffs[0] = a
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| 31 | ** coeffs[1] = b
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| 32 | ** coeffs[2] = c
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| 33 | ** coeffs[3] = d
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| 34 | ** coeffs[4] = e
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| 35 | ** coeffs[5] = f
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| 36 | **
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| 37 | ** The model is applied thus:
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| 38 | **
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| 39 | ** xp = a + b*xm + c*ym
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| 40 | ** yp = d + e*xm + f*ym
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| 41 | **
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| 42 | ** The residuals are (xp-xe) and (yp-ye).
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| 43 | **
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| 44 | ** If np is less than or equal to zero, no coordinates are
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| 45 | ** transformed, and the rms residuals are all zero.
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| 46 | **
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| 47 | ** See also slaFitxy, slaInvf, slaXy2xy, slaDcmpf
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| 48 | **
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| 49 | ** Called: slaXy2xy
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| 50 | **
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| 51 | ** Last revision: 31 October 1993
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| 52 | **
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| 53 | ** Copyright P.T.Wallace. All rights reserved.
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| 54 | */
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| 55 | {
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| 56 | int i;
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| 57 | double sdx2, sdy2, xp, yp, dx, dy, dx2, dy2, p;
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| 58 |
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| 59 | /* Initialize summations */
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| 60 | sdx2 = 0.0;
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| 61 | sdy2 = 0.0;
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| 62 |
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| 63 | /* Loop by sample */
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| 64 | for ( i = 0; i < np; i++ ) {
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| 65 |
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| 66 | /* Transform "measured" [x,y] to "predicted" [x,y] */
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| 67 | slaXy2xy ( xym[i][0], xym[i][1], coeffs, &xp, &yp );
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| 68 | xyp[i][0] = xp;
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| 69 | xyp[i][1] = yp;
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| 70 |
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| 71 | /* Compute residuals in x and y, and update summations */
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| 72 | dx = xye[i][0] - xp;
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| 73 | dy = xye[i][1] - yp;
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| 74 | dx2 = dx * dx;
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| 75 | dy2 = dy * dy;
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| 76 | sdx2 = sdx2 + dx2;
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| 77 | sdy2 = sdy2 + dy2;
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| 78 |
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| 79 | /* Next sample */
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| 80 | }
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| 81 |
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| 82 | /* Compute RMS values */
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| 83 | p = (double) gmax ( 1.0, np );
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| 84 | *xrms = sqrt ( sdx2 / p );
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| 85 | *yrms = sqrt ( sdy2 / p );
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| 86 | *rrms = sqrt ( *xrms * *xrms + *yrms * *yrms );
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| 87 | }
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