[pstricks] Two fail --- Backward solution?

[Hernando Diaz]

David Arnold escribió:
> All,
>
> I'm wondering why my initial conditions at -1.5 and 1.5 fail to draw  
> in the code below. Also, I am looking for a way to do solutions  
> backward in time.
>   
Hi David:
How about using

\def\negFunct{dup 3 exp exch sub neg}

and then solving

\psplotDiffEqn[linecolor=black,method=varrkiv,varsteptol=0.0001]{0} 
{2}{SomeSuitableInitialcondition}{\negFunct}
?

Best regards,
Hernando Diaz