Re: 2d vector fields

[Ethan M. <merritt@u.washington.edu>]

On Tuesday 17 April 2007 00:15, Pawel Cesar Sanjuan Szklarz wrote:
> Hi.
>=20
> Actually i need to send data from Gnuplot to Octave. Octave can send
> data to gnuplot, but I would like to send back to octave the
> information about the zoom and make a replot.

You don't need any new features in gnuplot to do that.
You can write the plot coordinates to an arbitrary file using

old syntax:
	set term push
	set term table
	set output "coords.dat"
	plot ...
	set term pop

New syntax (version 4.2):
	set table "coords.dat"
	plot ...
	unset table

See for example the original vector field example
	.../demo/vector.dem


You can even make this a pipe if you like, although I don't
know if this would help with Octave.

	set table "| my_program_expecting_an_input_stream"
	plot ...
	unset table

More likely you would open a named pipe for read access in Octave,
then trigger the gnuplot operation;  gnuplot would in turn open
the same named pipe for writing as above, as send the output back
to Octave.  You may find the examples on this page useful
(the ones under "Programming interfaces =E2=80=93 bidirectional interaction=
")
   http://gnuplot.info/links.html



>=20
> I will check the path:
>  [ gnuplot-Patches-1027032 ] Connect gnuplot_x11 to exterior application =
window
>=20
> maybe it is what i need.
>=20
> Thank you.
> Pawe=C5=82 Szklarz.
>=20
> 2007/4/17, Daniel J Sebald <dan...@ie...>:
> > Pawel Cesar Sanjuan Szklarz wrote:
> >
> > > Now I have the next ploblem: how to use external function to generate
> > > the values of the vector field?? why I need this: on my functions I
> > > solve a set equations to find the behavior of the robot. Thats why I
> > > am thinking about the pipe-feature.
> > >
> > > With the '+' filename it is possible in gnuplot to write the "x,y"
> > > values to evaluate in some file??
> > > May be it is possible to write the "x,y" grid, then run some process (
> > > in my case octave), and then use the results file to plot???
> >
> > The discussion of pipes and transfering data from Octave to gnuplot sho=
uld go to
> > the Octave list.  Octave currently sends data to gnuplot though a pipe.=
  The
> > Octave folks may be able to help you set something up in terms of trans=
ferring
> > data and the type of plot you'd like to generate.
> >
> > I've also update the patch
> >
> > [ gnuplot-Patches-1027032 ] Connect gnuplot_x11 to exterior application=
 window
> >
> > which uses a pipe created using TCL rather than C, but I see now that i=
sn't
> > anything you need.
> >
> > Dan
> >
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>=20

=2D-=20
Ethan A Merritt            Courier Deliveries: 1959 NE Pacific
Dept of Biochemistry
Health Sciences Building
University of Washington - Seattle WA 98195-7742