Thread Subject: Optimization of function with known and unknown variables

Hi all!

I'm working with the optmization toolbox for the first time
and I'm having some trouble.
I would like to find the minimum of this function:

sum(sqrt(x1-x2+dx).^2+(y1-y2+dy).^2))

x1,2 and y1,2 are known row vectors, dx and dy are unknown.

dx and dy should be scalars.

I read some stuff about eg. "fminunc" but it doesnt tell you
how pass known arguments (in this case x1,2 and y1,2) over
and only return dx and dy.

I hope I explained my problem properly.

Thanks a lot!
Volker

"Volker K" <klinkv.NOSPAM@yahoo.de> wrote in message
<fjrif3$adh$1@fred.mathworks.com>...
> Hi all!
>
> I'm working with the optmization toolbox for the first time
> and I'm having some trouble.
> I would like to find the minimum of this function:
>
> sum(sqrt(x1-x2+dx).^2+(y1-y2+dy).^2))
>
> x1,2 and y1,2 are known row vectors, dx and dy are unknown.
>
> dx and dy should be scalars.
>
> I read some stuff about eg. "fminunc" but it doesnt tell you
> how pass known arguments (in this case x1,2 and y1,2) over
> and only return dx and dy.
>
> I hope I explained my problem properly.

Use an anonymous function.

fun = @(dxdy) sum(sqrt(x1-x2+dxdy(1)).^2+(y1-y2+dxdy(2)).^2))

HTH,
John

"Volker K" <klinkv.NOSPAM@yahoo.de> wrote in message
news:fjrif3$adh$1@fred.mathworks.com...
> Hi all!
>
> I'm working with the optmization toolbox for the first time
> and I'm having some trouble.
> I would like to find the minimum of this function:
>
> sum(sqrt(x1-x2+dx).^2+(y1-y2+dy).^2))

That looks an awful lot like you're trying to fit a circle to data. If
that's what you're doing, I believe there are some submissions on the File
Exchange to do that.

> x1,2 and y1,2 are known row vectors, dx and dy are unknown.
>
> dx and dy should be scalars.
>
> I read some stuff about eg. "fminunc" but it doesnt tell you
> how pass known arguments (in this case x1,2 and y1,2) over
> and only return dx and dy.

Question 4.13 in the FAQ deals with passing additional parameters to
"function functions" like FMINUNC.

http://matlabwiki.mathworks.com/MATLAB_FAQ

--
Steve Lord
slord@mathworks.com