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# Formulas and Graphics ?????

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#### avr_nb

##### Newbie level 4
Hi all,

Is it possible to get a formula from a graphic table? Like when you get the response of a sensor, put all values in a graphic and must find a formula?

Thanks
Luiz

#### xxargs

##### Full Member level 4
avr_nb said:
Hi all,

Is it possible to get a formula from a graphic table? Like when you get the response of a sensor, put all values in a graphic and must find a formula?

Thanks
Luiz

Try search 'curve fitting' 'nonlinear regression', 'polynomial curves' etc. on google

One of many hits is:

https://en.wikipedia.org/wiki/Curve_fitting

https://mathworld.wolfram.com/LeastSquaresFitting.html

and one of many (but possibly not best) excel tutors:

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Many calculators, mathcad and mathematica and possibly excel have tool can help make coffecients from tabular number pair with linear and nonlinear regression ('curve fit' under statistic in most case) in first order (linear) and secondary order (exponent, logaritmic or power function depend of curve direction and 'bending' , or polynomial for higher order 'bumpy' curve)

For make first order (linear) and second order curve (with Pow, log or exp) with regression, you not need so many samples to make fairly good curve fit and uses widely to make 'trend lines' in marketing and business world, not only to make correction alghorithm for PTC or NTC temperature sensors...

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I think polynomial is easiest to handle in MCU-enviroment if you not have advanced float math-library with exp,log and pow-capability - but still need some kind of floating numbers arithmetic depend of wide scale between smallest and biggest used value.

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Points: 2