Direction field in gnuplot (was: some editing tools for maxima /Grumpy old man..)

On THU, 7 DEC 2006, Jaime E. Villate wrote:

[...]

> emacs, wxmaxima and xmaxima can be viewed as 3 alternate interfaces for
> Maxima, but xmaxima has also another task: if you want to plot graphs,
> I do not think we have a lisp-only alternative at this point. You
> either install gnuplot, or xmaxima. And there are some plots (plotdf)
> that cannot be made with gnuplot. That's what keeps me working on
> Xmaxima.
>

Can someone explain why direction field can't be done in gnuplot since
there are examples on Gnuplot website:

http://gnuplot.sourceforge.net/demo_4.2/vector.html

Thank you.
-- 
Leo