[Rd] Line breaks in mathematical formulae in Rd files (PR#13287)

[xieyihui at gmail.com]

Hi,

This is a problem about writing R documentation (R-exts 2.6). The
command "\deqn" defined in "Rd.sty" is:

\newcommand{\deqn}[2]{\[#1\]}

which will put mathematical formulae in the "displaymath" environment;
that means line breaks are not allowed (or will not be shown) in
formulae, but sometimes we do need multiple lines of formulae. One
solution is to write several equations using "\deqn", but I think to
change the definition of "\deqn" is better:

\newcommand{\deqn}[2]{\begin{eqnarray*}#1\end{eqnarray*}}

This will not change the pdfLaTeX output effect, moreover, line breaks
and alignments using "&" will be available in math formulae.

Regards,
Yihui
--
Yihui Xie <xieyihui at gmail.com>
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