2 Nov 2008 20:35

## A new pgfmath operator: sinc

Hello all,

Here is the code for the sinus cardinalis (sinc) function (see
http://en.wikipedia.org/wiki/Sinc_function), adding it to the pgfmath
parser. The argument is in radian.

But... It does not work and I don't understand why...

Christophe

\documentclass{minimal}

\usepackage{tikz,pgfplots}

\begin{document}

\makeatletter
\pgfmathdeclarefunction{sinc}{1}{%
\begingroup%
\expandafter\pgfmath <at> x#1pt\relax
\ifdim\pgfmath <at> x=0pt\relax
\def\pgfmathresult{1}%
\else
% First convert to radians x-> x r
% Take the sine x r -> sin(x r)
\pgfmathsin <at> {\pgfmathresult}%
% Divide by the argument sin(x r)/x
\pgfmathdivide <at> {\pgfmathresult}{#1}%
\fi
\pgfmath <at> smuggleone\pgfmathresult%
\endgroup}

\begin{tikzpicture}
\begin{axis}[xlabel=$x$,ylabel=$f(x)$,name=an axis]
\end{axis}
\end{tikzpicture}

\end{document}

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Gmane