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From: John H Meyers on 14 Mar 2010 16:21
On 3/14/2010 8:40 AM, Dave Hayden wrote:

> Once nice insight I had was that you don't actually need to know to
> thickness of the tape, diameter of the tape hub, tape speed etc. Once
> you know that it's a quadratic function, you can get the constant
> values empirically by just running a tape through and noting the
> (counter reading, elapsed time) pairs a couple of spots. A little
> math then derives the necessary constant terms to the quadratic
> equation. The program included a setup program for this purpose.

One could also use a standard polynomial regression, e.g. PREGR

http://www.hpcalc.org/search.php?query=pregr

The HP49/50 binary version of PREGR was loaded in Exact mode,
but should have been in Approximate mode; you should set
Approximate mode and then edit the program, once, after
installing it -- don't change anything, but just press
ENTER -- this will change all numbers to reals.

The original PREGR (docs and source) was also posted here:
http://groups.google.com/group/comp.sys.hp48/msg/c858942c7e7d2fbc?dmode=source

Virgil has also posted another program using LSQ:
http://groups.google.com/group/comp.sys.hp48/msg/f7824b0bb475c8a4

On the HP49/50 series, the following (much shorter :)
can also be used, once you have three good data points,
if you don't mind the exact fractions in the coefficients.
The first word below is "SigmaDAT" (recall the statistics matrix):

\GSDAT TRN XQ LAGRANGE

[r->] [OFF]
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