;
; iron_curvefit.hsp — カーブフィッティング (多項式 / 最小二乗法)
;
#ifndef __iron_curvefit_hsp__
#define __iron_curvefit_hsp__
#module iron_curvefit

; Linear fit: y = slope * x + intercept
#deffunc curvefit_linear array x, array y, int n, var slope, var intercept, \
	local sx, local sy, local sxy, local sxx, local i
	sx = 0.0 : sy = 0.0 : sxy = 0.0 : sxx = 0.0
	repeat n
		sx += x(cnt) : sy += y(cnt)
		sxy += x(cnt) * y(cnt)
		sxx += x(cnt) * x(cnt)
	loop
	slope = (double(n) * sxy - sx * sy) / (double(n) * sxx - sx * sx)
	intercept = (sy - slope * sx) / double(n)
	return

; R-squared
#defcfunc curvefit_r2 array x, array y, int n, double slope, double intercept, \
	local mean_y, local ss_res, local ss_tot, local pred
	mean_y = 0.0
	repeat n : mean_y += y(cnt) : loop
	mean_y /= double(n)
	ss_res = 0.0 : ss_tot = 0.0
	repeat n
		pred = slope * x(cnt) + intercept
		ss_res += (y(cnt) - pred) * (y(cnt) - pred)
		ss_tot += (y(cnt) - mean_y) * (y(cnt) - mean_y)
	loop
	if ss_tot == 0.0 : return 1.0
	return 1.0 - ss_res / ss_tot

#global
#endif