Gerry-
Bingo! Thanks.
-Jeff
At 03:01 PM 11/14/00 , you wrote:
>Jeff,
>
>I have a simple technique that may give you what you want. Try using the
>TREND GX
>(X-Utility | Filters | Polynomial). Use Trend Order = 1. The "Output trend
>channel" will contain a least-squares, best-fit straight line. The "Output
>residual channel" will contain the differences between the original data
>points
>and the straight line.
>
>Just do standard Geosoft channel statistics on the "Output residual
>channel" to
>get min, max and standard deviation of the differences. This approach has the
>added advantage of doing an entire database in one step. The Linear
>Regression
>GX will not work over multiple lines.
>
>Gerry Connard
>
>Jeff Gamey wrote:
>
> > Bill-
> >
> > Thanks for the outline, but my application is rather more rudimentary than
> > you give me credit for. I've got a simple spread of points that
> > approximate a straight line. I can use the linear regression function in
> > Geosoft to calculate slope and intercept, but I really want to know how
> > well the points fit that line and I can't find a Geosoft function to do it.
> >
> > -Jeff
> >
> > At 02:22 PM 11/14/00 , you wrote:
> > >Jeff:
> > >
> > >The methodology we have been using is to use the technique of
> bootstrapping,
> > >or resampling.
> > >
> > >Take your original line data, randomaly select a subset of all teh data
> > >points.
> > >Recalculate the slope.
> > >Repeat random resampling of the full data set
> > >Recalculate slope.
> > >
> > >Repeat process a number of times...
> > >
> > >You can then calculate the mean slope and derive an estimate of the error
> > >(standard deviation of that slope).
> > >This procedure gives you a depth estimate and a error on your depth
> > >estimate.
> > >
> > >Of course what it really serves to do is to emphasise that you really
> don't
> > >know very much about the depth of the longer wavelength portion of your
> > >spectrum since you only have a very small number of points in this portion
> > >of your curve.
> > >
> > >Bill Morris
> > >
> > >PS Kristi Markham one of my grad students gave talk on this subject at
> last
> > >years EGS conference, and is actively writing a paper on this subject.
> > >
> > >
> > >
> > >
> > >----- Original Message -----
> > >From: "Jeff Gamey" <[EMAIL PROTECTED]>
> > >To: <[EMAIL PROTECTED]>
> > >Sent: Tuesday, November 14, 2000 7:42 AM
> > >Subject: [geonet]: linear regression
> > >
> > >
> > > > I can run linear regression to get the slope and intercept of my
> data, but
> > > > I'd like a measure of error of fit to that line. Does anyone have
> a way
> > >to
> > > > do that apart from (a) manually inputting the slope and intercept
> into a
> > > > math expression for error of fit, then (b) calculating the std dev
> of the
> > > > error?
> > > >
> > > > Having it included in the linear regression GX would be ideal. If
> someone
> > > > wants to talk me through it, I'll try to modify it myself.
> > > >
> > > > *******************
> > > > * Jeff Gamey (4tj)
> > > > * Environmental Sciences Division [EMAIL PROTECTED]
> > > > * Oak Ridge National Laboratory (865) 574-6316 tel
> > > > * POBox 2008, Bldg 1505, MS6038 (865) 576-8646 fax
> > > > * Bethel Valley Rd., Oak Ridge, TN (865) 599-0820 cell
> > > > * 37831-6038
> > > >
> > > > _______________________________________________________
> > > > More mailing list info
> http://www.geosoft.com/support/listserv/index.html
> > > >
> > >
> > >_______________________________________________________
> > >More mailing list info http://www.geosoft.com/support/listserv/index.html
> >
> > *******************
> > * Jeff Gamey (4tj)
> > * Environmental Sciences Division [EMAIL PROTECTED]
> > * Oak Ridge National Laboratory (865) 574-6316 tel
> > * POBox 2008, Bldg 1505, MS6038 (865) 576-8646 fax
> > * Bethel Valley Rd., Oak Ridge, TN (865) 599-0820 cell
> > * 37831-6038
> >
> > _______________________________________________________
> > More mailing list info http://www.geosoft.com/support/listserv/index.html
>
>--
>*************************************************************************
>Northwest Geophysical Associates, Inc. http://www.nga.com
>Box 1063
>Corvallis, Oregon 97339
>voice: 541-757-7231 / fax 541-757-7331
>
>
>_______________________________________________________
>More mailing list info http://www.geosoft.com/support/listserv/index.html
*******************
* Jeff Gamey (4tj)
* Environmental Sciences Division [EMAIL PROTECTED]
* Oak Ridge National Laboratory (865) 574-6316 tel
* POBox 2008, Bldg 1505, MS6038 (865) 576-8646 fax
* Bethel Valley Rd., Oak Ridge, TN (865) 599-0820 cell
* 37831-6038
_______________________________________________________
More mailing list info http://www.geosoft.com/support/listserv/index.html
