Prev: Convex hull in 3D
Next: Strange slow performance on macbook pro
From: Tonja Krueger on 7 Aug 2010 01:30
I probably didn't explain properly:
I've got a function G(x), which is:
-(Sqrt[\[Pi]/2]*Erfc[x]*(-\[Mu]+Log[x]))/(2*Sqrt[\[Pi]]*\[Sigma])
The parameters mu and sigma are unknown. I would like to convert the formula so it has the Form:
x=.....
(So I kind of want to inverse the function). Is there a way to do so, with mu, sigma and x[i] not known?

Thanks for the help,
Tonja
___________________________________________________________
Neu: WEB.DE De-Mail - Einfach wie E-Mail, sicher wie ein Brief!
Jetzt De-Mail-Adresse reservieren: https://produkte.web.de/go/demail02

From: Bill Rowe on 8 Aug 2010 07:20
On 8/7/10 at 1:29 AM, tonja.krueger(a)web.de (Tonja Krueger) wrote:

>I probably didn't explain properly: I've got a function G(x), which
>is:

>-(Sqrt[\[Pi]/2]*Erfc[x]*(-\[Mu]+Log[x]))/(2*Sqrt[\[Pi]]*\[Sigma])

>The parameters mu and sigma are unknown. I would like to convert the
>formula so it has the Form: x=..... (So I kind of want to inverse
>the function). Is there a way to do so, with mu, sigma and x[i] not
>known?

What you have described above simply isn't possible. You are
asking for a symbolic expression that is F(x) such that F(G(x))
gives x. No such F(x) exists for your G(x). The only possibility
to invert G(x) is to use numerical techniques which require mu
and sigma to be given specific numerical values.


From: Sjoerd C. de Vries on 8 Aug 2010 07:20
Don't think you can do this algebraically. If mu and sigma are known
you can solve it numerically.

Cheers -- Sjoerd

On Aug 7, 7:30 am, Tonja Krueger <tonja.krue...(a)web.de> wrote:
> I probably didn't explain properly:
> I've got a function G(x), which is:
> -(Sqrt[\[Pi]/2]*Erfc[x]*(-\[Mu]+Log[x]))/(2*Sqrt[\[Pi]]*\[Sigma])
> The parameters mu and sigma are unknown. I would like to convert the formula so it has the Form:
> x=.....
> (So I kind of want to inverse the function). Is there a way to do so, with mu, sigma and x[i] not known?
>
> Thanks for the help,
> Tonja
> ___________________________________________________________
> Neu: WEB.DE De-Mail - Einfach wie E-Mail, sicher wie ein Brief!
> Jetzt De-Mail-Adresse reservieren:https://produkte.web.de/go/demail02


 | 
Pages: 1
Prev: Convex hull in 3D
Next: Strange slow performance on macbook pro