// polyfit.h    polyfit(pwr, n, x, y, p)
// i=0; i<n     y[i] = p[0] + p[1]*x[i] + p[2]*x[i]^2 + ... x[i]^pwr
// needs  #include "simeq.h" // compile with  simeq.c

void polyfit(int pwr, int n, double x[], double y[], double p[]);