The objective of Homework 5 is to trace codes of two R packages and report
your findings. Some guys copied descriptions from R documentations or other
references, though with re-organization. Since Homework 6 has similar
requirements, here we announce the rule: Quotations are allowed only if they
are necessary and explicitly stated (for example, the following is
quoted from [1]: "..."), while copying, even with re-organization,
is forbidden.