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Curve Fit Problem

MoeSzyslak
4-Participant

Curve Fit Problem

Hi All -- I'm doing what I thought was a very straightforward curve fit with Minerr, but I am getting strange results. Any ideas? By the way, there may be functions that better fit the data than the one I supplied, but I am constrained by external forces to use that equation. Thanks.

Matt
3 REPLIES 3

Typical. You are fitting the data directly, but you are plotting on a log scale. The log scale accentuates the small errors, so that they look large (although they are in fact very small). If you want something that looks like a fit on a log scale, fit the logs of the data.

Your data also shows a lot of scatter. Almost like you have mixed in two different data sets, the upper values and the lower values. Don't read too much into whatever values you get from minerr.
__________________
� � � � Tom Gutman

Not so bad. I replace the theoretical formula with a quotient of polynomials and smooth the raw data. This gets a closer fit over most of the range.

If I recall it, the effect of snall errors was avoided around 1916 AD by the Langmuir/Blodgett "normal fit" algorithm, wherein
vertical least squares was replaced by a normal (tangent)assay.
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