Piece Wise Linear Fitting

Dec 12, 2013 4 Replies

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Jim Thompson 12 years ago

Another dawning while doodling at the beauty shop...

... a way to join line segments easily to form PWL's, while maintaining all derivatives at the joining points.

(Using my TANH version of greater than, less than... I'm working on refining its coefficients to match segment slopes so there's no "peaking" :-) ...Jim Thompson

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| 1962 | I love to cook with wine. Sometimes I even put it in the food.

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Tim Williams 12 years ago

Try regular hyperbolae. The derivatives exist... just take care not to divide by zero (which can happen with tanh too, and probably at analogous points, for analogous reasons).

Tim

-- Seven Transistor Labs Electrical Engineering Consultation Website:

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"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

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Phil Hobbs 12 years ago

Division by zero computing tanh of a real number? That would take talent. Care to elaborate?

Cheers

Phil Hobbs

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Tim Williams 12 years ago

Maybe it was atanh, but it's not the function of a real number, it's the derivative that causes problems. Certain people here swear by this for continuous limiter functions in SPICE, but I've found they can go batty rather often.

Incidentally, The Internet doesn't know that degenerate circuits aren't the only condition that can create singular matrices.

Tim

Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com

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Jim Thompson 12 years ago

All derivatives of TANH exist and don't go "batty". You must be thinking of some other function. ...Jim Thompson

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