One can determine g ( r ) indirectly (via its relation with the structure factor S ( q ) ) using neutron scattering or x-ray scattering data. The technique can be used at very short length scales (down to the atomic level) but involves significant space and time averaging (over the sample size and the acquisition time, respectively). In this way, the radial distribution function has been determined for a wide variety of systems, ranging from liquid metals to charged colloids. Going from the experimental S ( q ) to g ( r ) is not straightforward and the analysis can be quite involved.