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- Error -20116 finding quadradic fit

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03-16-2018 05:58 PM - edited 03-16-2018 06:00 PM

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Here's the error:

Error -20116 occurred at Bad Regression.vi Possible reason(s): Analysis: Feasible solution not found.

Here's my code:

Here's my XY data:

7280 1.22858E+7 7312 1.25469E+7 7344 1.25722E+7 7376 1.21155E+7 7408 1.13621E+7

I noticed that if I scale down the Y, everything works out OK which tells me maybe I need to normalize my data some how. Is there some standard data prep and unprep for regressions like this?

03-16-2018 06:17 PM - edited 03-16-2018 06:19 PM

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Why are you using bisquare?

The constant term is 1 but x^2 is >10^14, making the problem __ill conditioned__. The matrix elements differ by >10^14 so there are not enough bits to sort it out.

03-16-2018 06:54 PM

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Sorry, I take that back because you have x and y swapped (mislabeled!). Your x is 7280-7480, i.e. a small relative range. You get better results if you e.g. subtract the mean from x, for example. No scaling needed.

03-16-2018 06:59 PM

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03-16-2018 08:09 PM

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