Re: Contour plots

[Harald H. <h.h...@tu...>]

On Thu, 27 Jan 2005, Daniel J Sebald wrote:

> Ethan Merritt wrote:
> >On Tuesday 25 January 2005 05:04 am, Hans-Bernhard Broeker wrote:
> >>Daniel J Sebald wrote:
> >
> >>Right, it can't.  The main problem being that it's an absolute beast of
> >>a problem to figure out *where* to put such labels
> >
> >I agree that it is difficult.
>
> I would too.  However, might it be possible to use some simple algorithm
> that does an OK job in most cases?  The worst case scenario is when the
> contours are rather small oval shapes, or rather close together.  But if
> it is unacceptable to the user, then he or she could turn off
> annotation.  Rather than an optimization problem where we, say, pick a
> trajectory with the smallest gradient (i.e., largest spacing between
> contours), could we just pick some line for which to intersect as the
> spot to pick the label text?  (Intersecting with lines is a not so
> difficult thing.)

I think this is a good idea. Another could be that the user gives a curve
in x-y space either by data points or by a parametric function. The labels
for the contours could then positioned where the contours and the given
line intersect.

> >On the other hand, the mousing code is now versatile enough
> >that you could write a script to add the labels interactively.
> >I can imagine a semi-automated mode in which you click twice,
> >once at point X above and once and point Y above, and the script
> >proceeds to add a label on each intervening contour.
>
> Ethan's mouse idea could work, but I think once one does that, people
> will start asking for more and more mouse features to the point where
> gnuplot becomes GUI oriented.  Which might be OK.

I dislike features that are only available by interaction of the user.
What I does in most cases is to write a gnuplot file that is invoked by
the command line. If you have to use the mouse after each small change it
is really not good to me. Thus I think either an automatic or a
script-driven possibility to put these labels has to exist. That does not
mean that an additional mouse positioning was a bad idea.

Harald

-- 
Harald Harders
h.h...@tu...
http://www.harald-harders.de