drawing a curve and find the formula
2

Question

drawing a curve and find the formula

robyengIT (Mechanical)

(OP)

8 Mar 23 18:35

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 (Civil/Environmental) · Answer 1 · 2023-03-09 02:10:39

Yes, in Excel.
https://mathstat.slu.edu/~may/ExcelCalculus/sec-1-...

robyengIT (Mechanical) · Answer 2 · 2023-03-09 07:02:21

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

fel3 (Civil/Environmental) · Answer 3 · 2023-03-09 17:40:18

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 (Structural) · Answer 4 · 2023-03-10 05:55:43

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

https://res.cloudinary.com/engineering-com/raw/upload/v1678427617/tips/FITCURVE_par2uk.BAS

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 (Structural) · Answer 5 · 2023-03-10 06:07:59

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 (Mechanical) · Answer 6 · 2023-03-10 14:46:34

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

IDS (Civil/Environmental) · Answer 7 · 2023-03-20 08:33:22

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 (Mechanical) · Answer 8 · 2023-04-10 02:47:15

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

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drawing a curve and find the formula
2