MATLAB Central Newsreader - curve fitting

curve fitting

Mohammad Monfared — Mon, 03 Nov 2008 10:57:02 -0500

Hi everybody,
I'm trying to fit a curve of a custom equation to my data using matlab, but I can't get any answer. Could anyone suggests where is the problem.

x1=[0 2 50 106 250 500 1000 2000];
y1=[0 0.03 0.17 0.279 0.735 0.921 0.994 1.002];
s = fitoptions('Method','NonlinearLeastSquares',...
               'Lower',[0,0,0,0],...
               'Upper',[1000,10,10,10],...
               'Startpoint',[100,2,1,1]);
fredfitype=fittype('(1/log(exp(1)+(ag/x)^ng)^mg)*(1-(log(1+(dg)/x)/log(1+dg)))^7','options',s);
[c0] = fit(x1,y1,fredfitype);

I know from SPSS software that the answer is:
ag=250 ; ng=2.944 ; mg=1.2 ; dg=3.059 ;

thanks so much,

Re: curve fitting

dcorrea — Mon, 03 Nov 2008 13:22:00 -0500

Hello

Can you try to use CURVE FITTING Tool (Interface Graphic)

>> cftool

Greetings
David C.

On Nov 3, 5:57=A0am, "Mohammad Monfared" <gohardo...@gmail.com> wrote:
> Hi everybody,
> I'm trying to fit a curve of a custom equation to my data using matlab, b=
ut I can't get any answer. Could anyone suggests where is the problem.
>
> x1=3D[0 2 50 106 250 500 1000 2000];
> y1=3D[0 0.03 0.17 0.279 0.735 0.921 0.994 1.002];
> s =3D fitoptions('Method','NonlinearLeastSquares',...
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'Lower',[0,0,0,0],...
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'Upper',[1000,10,10,10],...
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0'Startpoint',[100,2,1,1]);
> fredfitype=3Dfittype('(1/log(exp(1)+(ag/x)^ng)^mg)*(1-(log(1+(dg)/x)/log(=
1+dg=AD)))^7','options',s);
> [c0] =3D fit(x1,y1,fredfitype);
>
> I know from SPSS software that the answer is:
> ag=3D250 ; ng=3D2.944 ; mg=3D1.2 ; dg=3D3.059 ;
>
> thanks so much,

Re: curve fitting

Mohammad Monfared — Mon, 03 Nov 2008 16:48:02 -0500

I've tried it too (with larger numbers for MaxIteration and Fun-eval, parameters) , but no answer !

thanks,
Mohammad M.

dcorrea <david.correa@gmail.com> wrote in message <f5ab4c87-65da-4dfa-aa4f-196f220acfd4@v16g2000prc.googlegroups.com>...
>
> Hello
>
> Can you try to use CURVE FITTING Tool (Interface Graphic)
>
> >> cftool
>
> Greetings
> David C.
>
>