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Re: Approximation of a Function

  • To: mathgroup at
  • Subject: [mg33474] Re: Approximation of a Function
  • From: Thomas Burton <tburton at>
  • Date: Fri, 22 Mar 2002 04:07:09 -0500 (EST)
  • Sender: owner-wri-mathgroup at


You can choose the interval, model, and fitting criterion, but you will be
stuck the goodness of fit determined by these choices. Here I choose your
suggested model, the interval [0.1, 1], and default measure of fit,
unweighted sum of squares of deviations, over equally spaced points on the

In[349]:= <<Statistics`NonlinearFit`

In[378]:= Clear[a,b,c,f,g,c1,c2,x]

In[379]:= f[x_]:=a*x+b*x^2+c*x^3

In[384]:= g[x_]:=c1 x^c2

In[391]:= Block[{a=1,b=2,c=3},
Out[391]= 5.92041141648034*x^2.124715956132496

Tom Burton

On 3/21/02 6:36 AM, in article a7cr53$hsn$1 at, "Zsolt Regaly"
<rezso at> wrote:

> Hi MathGroup!
> Can somebody to help me to find a solution of approximation of a function?
> I have a function f[x_]:=a*x+b*x^2+c*x^3, where a,b,c are known numbers. I
> would like to find a simplier function for f, for example g[x]=c1 x^c2 at an
> given interval with specified precision. How can I find the numbers c1 and c2?
> Thanks for Help, Zsolt Regaly.

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