Re: Contour plots

[Daniel J S. <dan...@ie...>]

Harald Harders wrote:

>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.
>  
>

I was thinking that!  :-)  But I thought no one else would like that idea.

>>>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.
>

I agree with that.  Mouse is good for zooming, no doubt there.  But it 
is always nice to build graphs from a file without any 
interaction--unless the labels could be stored somehow.  But still...

Dan