General ⇒ [PStricks] differentials equations

[yesugei]

Hello everybody,

I am trying to use differentials tools with the package pstricks-add and I have some issues :

I don't really understand the way to define equations. My equations are :

Code: Select all

$\left\{\begin{array}{l}
\frac{dx}{dt}=\lambda_1 x\\
\frac{dy}{dt}=\lambda_2 y
\end{array}\right.$

with $\lambda_i$ fixed in $\mathbb{R}*$.

there is my code to draw it :

Code: Select all

\def\Func{-y[0]/4|y[1]/2}%
\psset{linewidth=0.5pt, plotpoints=50,algebraic=true}%,
\begin{pspicture}(-5,-5)(5,5)
\psclip{\psframe[linestyle=none](-4.95,-5)(4.95,5)}%
\multido{\rx =-5+1}{10}{%
\multido{\ry=-5+1}{10}{%
\psplotDiffEqn[linecolor=red,arrows=->,ArrowInside=->,ArrowInsidePos=0.50,arrowscale=1.5]{0}{5}{\rx \space\ry}{\Func}%
\psplotDiffEqn[linecolor=blue,arrows=->,ArrowInside=->,ArrowInsidePos=0.90,arrowscale=1.5]{0}{-5}{\rx\space\ry}{\Func}
}%
}%
\psaxes[labels = none, linewidth =0.8pt ]{->}(0,0)(-5,-5)(5,5)%
\endpsclip
\end{pspicture}

My main goal is to have the solution drawn with a little arrow which indicate the evolution with the time.

For the arrow it is nearly good (except for the second "\psplotDiffEqn" which draw them in the wrong way) but the drawing i get is very bad ! it is absolutely not the good function !


May could you help me?

thanks.

Yesugei.

ps: please forgive my bad english...

[yesugei]

I have found how to correct the drawing : i must set this options : "whichabs = 0,whichord =1".

but the way where pstricks places the arrow is bad : an arrow for each plot point! that's meanning 200 arrows ! it is to much !! i just need 1 or 2 arrow by curve!!

do you know how to do it?

Yesugei.