drawing a curve and find the formula 2

[robyengIT]

Is there any possibility to draw a line by points and find a polynomial (??) formula that can reproduce the original line so that to search for intermediate coordinates ?

 

[CarlB]

Yes, in Excel.

https://mathstat.slu.edu/~may/ExcelCalculus/sec-1-5-IntroBestFitCurves.html

 

[robyengIT]

Thanks. I knew this solution and I did. Now I will check whith some of the instructions I didn't know. Thks again

 

[fel3]

If you need more curve fitting options than Excel provides, you can try CurveExpert Basic or CurveExpert Pro:

https://www.curveexpert.net/

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[dik]

If you can make heads or tails of it... old basic library file attached.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1678427617/tips/FITCURVE_par2uk.BAS[/url]

There was an HP publication on curve fitting... I'll see if I can dig it up... I may have the original, and I know I scanned it... It had numerous approaches to curve fitting for various types of curves and various types of data.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

these were the curve functions...

Stuff I did 30 years ago... used BASIC in lieu of C... the Microsoft Basic math library used the Fortran library and was faster than the C library. With 8088 processors, it mattered back then...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[robyengIT]

Fel3 : I bought the pro version. Absolutely fine. THANKS

 

[IDS]

Several articles on curve-fitting with Excel here:

https://newtonexcelbach.com/?s=fit+polynomial

Including buit-in functions, Alglib, and Python functions.



Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[IanVG]

Free and basic version available online is WebPlotDigitizer; I'm using it to recreate pump curves from old printouts. Link here.