Vinodh Kumar wrote:

>

> Number One:

> =========

> I know its a 100% offline post.But seeing the diversity of the domain from

> which people are participating,

> I would like to post this question here.Pardon me.At the least, u can guide

> me to the proper newsgroup.Thanks.

>

> Number Two:

> =========

> I want to draw a curve for a set of observations(i.e, x,y pairs) using

> Quadratic fit using Least Square method.

> I do not what is the step1, step2, step 3 i mean alogorithm for this

> process.Any helps will be gratefully appreciated.

>

> Regards,

> Vinodh Kumar P
Well, i don't know what are your real aims. We use least square method

to fit with a model curve.

By example, you can by this method find the straight line who is the

nearest from a set of points.

It is very used in physics when you want to find numerically the

parameters of a linear law. You

can also use least square method to find the nearest parabole, cubic

... curve, which is the nearest from your points.

You compute by this way the coefficients a,b,c so that y=a x² + b x +c

is the nearest

parabol from your points.

Then you have to minimize the functionnal J = Sum_i( (y_i - a*x_i²+

b*x_i +c)^2) where (x_i,y_i) is the set of points

If your aim is to smooth a set of edges, you can use smooth techniques

like splines. Especially cubic splines are very nice.

You ensure by using cubic splines that your curve will pass by your sets

of points, and the curve is smooth. I joined a documentation

about splines

http://kr.cs.ait.ac.th/~radok/math/mat7/step28.htm
http://math.arizona.edu/~restrepo/47...ea/node35.html
--

Marc Durufle

Inria Rocquencourt

Tel : 01 39 63 56 27

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