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Re: Re: ListCurvePathPlot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95982] Re: [mg95942] Re: ListCurvePathPlot
  • From: "David Park" <djmpark at comcast.net>
  • Date: Sat, 31 Jan 2009 01:15:22 -0500 (EST)
  • References: <gls253$hq3$1@smc.vnet.net> <14852987.1233315269397.JavaMail.root@m02>

This is a case where better documentation would be a definite aid, not only
to users but also to WRI. Sometimes I have the impression that one person
writes the routine and another person documents it in a one-way irreversible
process. The documentation should have some 'practical' examples, not just
formalistic. ListCurvePathPlot may have some very good uses. We just don't
see what they are.

If a routine is difficult to explain or run with practical examples in the
documentation, then it may contain errors or be ill designed, and should go
back to the design and coding phase.


David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/  


From: Jens-Peer Kuska [mailto:kuska at informatik.uni-leipzig.de] 

Hi,

and more over, it does it wrong because I try your example with

data = Table[
    RandomReal[{.8, 1.2}] {Cos[t], Sin[t]}, {t, 0, 2 \[Pi] - 2 \[Pi]/6,
      2 \[Pi]/32}];

got the data
data-{{0.899074, 0}, {0.931267, 0.185241}, {1.10439, 0.457454}, {0.955484,
   0.638434}, {0.795648, 0.795648}, {0.547609, 0.819554}, {0.318697,
   0.769402}, {0.232974, 1.17124}, {0, 1.18407}, {-0.207593,
   1.04364}, {-0.459194, 1.10859}, {-0.639312, 0.956798}, {-0.664321,
   0.664321}, {-0.953214, 0.636917}, {-0.966874, 0.400492}, {-0.893422,
    0.177713}, {-1.02206,
   0}, {-1.09618, -0.218044}, {-0.995037, -0.412158}, {-0.775199, \
-0.517972}, {-0.722555, -0.722555}, {-0.643561, -0.963157}, \
{-0.373253, -0.901112}, {-0.232702, -1.16987}, {0, -0.93512}, \
{0.189465, -0.952506}, {0.338656, -0.817588}};

and the result is

ListCurvePathPlot[data, InterpolationOrder -> 3, Axes -> False,
  InterpolationOrder -> 16]

not curved, not interpolated  and broken into *two* pieces.

May be you don't understand the function because it is buggy and useless ...

Regards
   Jens

David Park wrote:
> I don't understand the new ListCurvePathPlot, which the Help page says:
> "attempts to reconstruct smooth curves defined by the specified set of
> points."
> 
>  
> 
> This plot routine also has the option: InterpolationOrder. And the word
> "Curve" appears not only in the name but repeatedly in the descriptions.
> But look at the following example:
> 
>  
> 
> data = Table[
> 
>    RandomReal[{.8, 1.2}] {Cos[t], Sin[t]}, {t, 0, 2 \[Pi] - 2 \[Pi]/6,
> 
>      2 \[Pi]/6}];
> 
> ListCurvePathPlot[data,
> 
>  InterpolationOrder -> 3,
> 
>  Axes -> False]
> 
>  
> 
> I don't see anything "smooth" or "curvy" about the results!  So it seems
> that these terms are a misdirection in understanding the use of the
routine.
> It appears that what the routine actually does is reorder the points to
give
> some simpler line (not curve) than the original set of points. But what is
> the criterion for this? Is this some well know computational geometry
> algorithm? Was InterpolationOrder included as an option by mistake? Did
the
> implementation change from the original intention? What is the purpose of
> the routine? What is the relation of this and the spline functions?
> 
>  
> 
> David Park
> 
> djmpark at comcast.net
> 
>  <http://home.comcast.net/~djmpark> http://home.comcast.net/~djmpark/  
> 




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