/*

linear least squares, rank = llsq( x, y, m, c, n)

Determines n coefficients c such that y ~= c0 + c1*x + c2*x*x + c3*x*x*x + ...

Solves the equation U'c = y for c using SVD, where U' is the m-by-n matrix
evaluated at the m x values:

        1  x0  x0*x0  x0*x0*x0  ...
  U' =  1  x1  x1*x1  x1*x1*x1  ...
        1  x2  x2*x2  x2*x2*x2  ...
        ...
*/

int llsq( double x[], double y[], int m, double c[], int n);