Modified Distance 1

Regarding why the richardson performs well on c5, c6 and c8, I guess
it’s because c5, c6 and c8 have clearer quadratic (linear?)
relationship with the distance. See graph 1_1. So I tried to ignore the
middle two dimensions of observation vector. It does makes c3 has
better quadratic relationship with distance, see graph 1_2, but it
doesn’t improvement the performance on c3, see 1_3.