# Re: st: RE: Brute force

 From David Airey To statalist@hsphsun2.harvard.edu Subject Re: st: RE: Brute force Date Mon, 16 Mar 2009 15:34:40 -0500

```.

This might be what he is asking...?

http://cran.r-project.org/web/packages/nls2/nls2.pdf

-Dave

On Mar 16, 2009, at 3:08 PM, Verkuilen, Jay wrote:

```
```I'm not sure what you mean by "brute force."

This is a nonlinear regression, and you haven't fully specified the
model. It's not obviously linearizable so you'll need to use nonlinear
least squares, -nl-, assuming that the model is really

Ai=B0*Ci*(Di^B1) + ei,

where ei is a Gaussian error. If not, you need to figure out what the
error term is. Multiplicative error would be

Ai=B0*Ci*(Di^B1)*exp(ei).

```
I'd be worried about identification so you should make very sure to give
```good starting values.

```
Also, this model may not be appropriate for all variables. In particular if Ai, Ci, and Di aren't ratio scales (e.g., time, mass, etc.) I am not
```sure it makes any sense at all.

JV

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Shun
Chonabayashi
Sent: Monday, March 16, 2009 3:51 PM
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: RE: Brute force

Thank you so much for your replies.

```
Then, for example, if I have observations of variables Ai, Ci and Di and want to obtain the best estimates for constants B0 and B1 in the formula
```below, do you think I can apply "brute force"? If so, could you let me
know
how to command this in Stata? Thanks for your time.

Ai=B0*Ci*(Di^B1)

Shun

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Monday, March 16, 2009 2:15 PM
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: RE: Brute force

Jeph is based in the USA. That may not be evident from his email

I think we agree, w.r.t. Shun's question, is that there isn't a
prescription
for applying brute force, any more than there is a prescription for
elegance
or simplicity.

Nick
n.j.cox@durham.ac.uk

Jeph Herrin

This may be a transatlantic distinction, but on this side of the pond,
"brute force" is often both admirable and desirable in all respects
except
```
efficiency. That is, the brute force method may be the best approach but
```too
costly (in terms of time or resources) to implement.
In analysis, at least; in areas such as diplomacy it indeed lacks an

Nick Cox wrote:
```
```This question probably arises as a understandable puzzle about
```
```someone's
```
```English usage, possibly mine!

Some approach may be described as "brute force", but that means only
that the technique will work, but is otherwise not admirable or
desirable.

There isn't a converse recipe for "brute force".

Some idea of context would be helpful.

Nick
n.j.cox@durham.ac.uk

Shun Chonabayashi

```
Could anybody explain how to do "brute force" in Stata or refer to any
```
```
```page which explains about it? Thanks.

```
```
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