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Fix sign-error on slope for RMA regression #3634

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Merged
merged 1 commit into from
Jul 10, 2020
Merged

Fix sign-error on slope for RMA regression #3634

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4 changes: 3 additions & 1 deletion src/gmtregress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -743,13 +743,15 @@ GMT_LOCAL double gmtregress_LSxy_regress1D_basic (struct GMT_CTRL *GMT, double *
GMT_LOCAL double gmtregress_LSRMA_regress1D (struct GMT_CTRL *GMT, double *x, double *y, double *w[], uint64_t n, double *par) {
/* Basic LS RMA orthogonal regression with no weights [Reference?] */
uint64_t k;
double sx, sy, scale;
double sx, sy, scale, r;
double *U = gmt_M_memory (GMT, NULL, n, double), *V = gmt_M_memory (GMT, NULL, n, double), *W = gmt_M_memory (GMT, NULL, n, double);
gmt_M_memset (par, GMTREGRESS_NPAR, double);
(void)gmtregress_demeaning (GMT, x, y, w, n, par, U, V, W, NULL, NULL);
r = gmt_corrcoeff (GMT, U, V, n, 1);
sx = gmt_std_weighted (GMT, U, w[GMT_X], 0.0, n);
sy = gmt_std_weighted (GMT, V, w[GMT_Y], 0.0, n);
par[GMTREGRESS_SLOPE] = sy / sx;
if (r < 0.0) par[GMTREGRESS_SLOPE] = -par[GMTREGRESS_SLOPE]; /* Negative correlation means negative slope */
par[GMTREGRESS_ICEPT] = par[GMTREGRESS_YMEAN] - par[GMTREGRESS_SLOPE] * par[GMTREGRESS_XMEAN];
par[GMTREGRESS_ANGLE] = atand (par[GMTREGRESS_SLOPE]);
for (k = 0; k < n; k++) /* Here we recycle U as y-residual e */
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