Hi,

I used the file Bezier curve function from the file exchange:

http://www.mathworks.co.uk/matlabcentral/fileexchange/30759-bezier-curve-plotter

and it seems that it plots the curve correct. Does anybody know how can I see the equation which describes the curve that you plot?

Thanks
Yannos

"Yannos M" wrote in message <jruq7j$req$1@newscl01ah.mathworks.com>...
> Hi,
> 
> I used the file Bezier curve function from the file exchange:
> 
> http://www.mathworks.co.uk/matlabcentral/fileexchange/30759-bezier-curve-plotter
> 
> and it seems that it plots the curve correct. Does anybody know how can I see the equation which describes the curve that you plot?
> 

This is perhaps the most common misunderstanding
that people have about spline models.

You can't. Its a spline. There is NO simple function
that can be written down for that curve. At best,
one could write down a long list of coefficients of
polynomial segments, which will be of no use to
you or anyone else.

John

John,

Thanks, you are right. I'm just trying to find an equation which will give me the coordinates of a curve or an arc which is tangent to 2 lines.

Yannos


"John D'Errico" <woodchips@rochester.rr.com> wrote in message <jrutav$8v7$1@newscl01ah.mathworks.com>...
> "Yannos M" wrote in message <jruq7j$req$1@newscl01ah.mathworks.com>...
> > Hi,
> > 
> > I used the file Bezier curve function from the file exchange:
> > 
> > http://www.mathworks.co.uk/matlabcentral/fileexchange/30759-bezier-curve-plotter
> > 
> > and it seems that it plots the curve correct. Does anybody know how can I see the equation which describes the curve that you plot?
> > 
> 
> This is perhaps the most common misunderstanding
> that people have about spline models.
> 
> You can't. Its a spline. There is NO simple function
> that can be written down for that curve. At best,
> one could write down a long list of coefficients of
> polynomial segments, which will be of no use to
> you or anyone else.
> 
> John

"Yannos M" wrote in message <jrv69s$ga8$1@newscl01ah.mathworks.com>...
> John,
> 
> Thanks, you are right. I'm just trying to find an equation which will give me the coordinates of a curve or an arc which is tangent to 2 lines.
>

Ok, so a cubic polynomial will suffice, as long as the
slope is not infinite at either point. If that were true,
it is still possible to arrive at a parametric solution.

You know the points in question, and the slopes at
those points. So you have 4 pieces of information,
enough to generate the single cubic segment, since
a cubic is defined by 4 coefficients. A Hermite cubic
will suffice.

http://math.fullerton.edu/mathews/n2003/HermitePolyMod.html

John