Usage: <tt>input = [ <i>ng  gID_1  gID_2  &hellip; gID_ng</i> ] RtoR0_by_group</tt>

<p>
Make a copy of the <tt>R</tt> array to <tt>R0</tt> for all atoms whose
group id (<tt>group[i]</tt>) matches one of those specified by <tt>input</tt>.

<p>
Also see <tt>RtoR0</tt>.

