[pstricks] \psplotDiffEqn (pstricks-add)
Dominique RODRIGUEZ
dominique.rodriguez at waika9.com
Wed Jun 3 14:56:20 CEST 2009
Hello,
> I want to translate the set of differential equations of the 'spiral of
> cornu' example from the pstricks-add manual, Section 36.2 from algebraic
> into Postscript syntax.
You are quite malicious ! I wrote the ps to alg translator to easyly describe the
description using the natural algebraic notation !
> >From the Postscript reference I know that the sin and cos operators
> want angles in degrees as their argument. Hence, I have to multiply the
> arguments of sin and cos, as given in Eqs. (4) and (5) on Page 170 of
> pstricks-add-doc.pdf, by 180/Pi which led me to the following formulation:
>
> \documentclass{article}
> \usepackage{pstricks-add}
>
> \begin{document}
> \psset{unit=8}
> \begin{pspicture}(1,1)\psgrid[subgriddiv=5]
> \psplotDiffEqn[
> whichabs=0,whichord=1,linecolor=red,method=rk4,
> % algebraic=true,
> plotpoints=500,showpoints=true
> ]{0}{10}{0 0}{
> % %algebraic
> % cos(Pi*x^2/2)|sin(Pi*x^2/2)
> %Postscript
Here add : pop pop
> x dup mul 2 div 180 mul cos %% dx/dt
> x dup mul 2 div 180 mul sin %% dy/dt
> }
> \end{pspicture}
> \end{document}
The solver calls the function description with the vector on the stack : x y,
and the description leave dx dy at the end, if you don't use x and y just drop them.
Bye
Dominique
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