[pstricks] drawing implicit (polar) plot

[Herbert Voss]

Arnaud Schmittbuhl wrote:

> This equation is the one we get by studying flow around a cylinder.
> The result can be seen here 
> 
> http://www.mecaps.cict.fr/cfd/ifm/cylinder.gif

ok, understood

Herbert


\listfiles
\documentclass[a4paper]{article}
\usepackage{pstricks}
\usepackage{pstricks-add}
\usepackage{multido}
\def\func{%
     const x sin dup mul 3 mul div neg /p exch def
     p abs sqrt neg /r exch def
     -0.5 /q exch def
     p 0 lt {
       p dup mul p mul q dup mul add 0 le {
         q r 3 exp  div arccos
         3 div cos r dup add neg mul
       }{
         q r 3 exp div arch
         3 div cosh r dup add neg mul
       } ifelse
     }{
       q r 3 exp div arsh
       3 div sinh r dup add neg mul
     } ifelse
}
\begin{document}

\begin{pspicture*}(-5,-2.5)(5,2.5)
   \pstVerb{
     /e 2.718281828459045 def
     /arccos { dup dup mul neg 1.0 add sqrt exch atan } def
     /sinh { dup e exch exp exch neg e exch exp sub 2 div } def
     /cosh { dup e exch exp exch neg e exch exp add 2 div } def
     /arsh { dup dup mul 1 add sqrt add ln } def
     /arch { dup dup mul 1 sub sqrt add ln } def
   }
   \psaxes(0,0)(-5,-2.5)(5,2.5)
   \psset{plotpoints=360,linewidth=0.1pt,polarplot=true,linecolor=blue}
   \multido{\rA=0.05+0.05}{20}{
     \psplot{1}{179}{%
       /const \rA\space def
       \func
     }
     \psplot{181}{359}{%
       /const \rA\space def
       \func
     }%
   }
\end{pspicture*}

\end{document}




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