How to linearly interpolate from a table

Forum|Forum|5 years ago
April 15, 2021
2 replies
3941 views

I need to linearly interpolate from a table, which I attached with some examples.
I appreciate any help... Thanks a lot!

1_Table_Interpolation.zip

Best answer by LucMeekes

We had almost feared you had lost interest.

Anyway, I guess what you need can still be done with linterp, it just requires an addition to the table at both sides you add a column with repeating values. See attached.

Success!
Luc

L

LucMeekes

23-Emerald IV

Did you already have a look here?

https://community.ptc.com/t5/PTC-Mathcad/Interpolation-of-Table-Values/td-p/721321

Anyway, attached is a sheet that should work for you.

Success!
Luc

1_LM_20210415_Table_Interpolation.zip

E

Eng_ReyD_497

Author

12-Amethyst

Thanks @LucMeekes and @Fred_Kohlhepp for your efforts! ... Nice work

Sorry, I was away for over a week, and I did not have the chance to check earlier.

The solution that @LucMeekes has provided works perfect, BUT, I do not want to extrapolate beyond the boundaries. Just stick to the minimum or the maximum if the interpolated value goes beyond the limits. Otherwise works fantastic!

The solution that @Fred_Kohlhepp has provided works perfect for not performing the extrapolation, but works only the SiteClass "B" and does not change automatically if I change the class to "D" for instance.
Looks like the row position is "hard coded" but I need it more dynamic to perform the lookup by changing the SiteClass to any other letter in the list...

Thanks guys, I learn from both of you!

L

LucMeekes

Answer

23-Emerald IV

We had almost feared you had lost interest.

Anyway, I guess what you need can still be done with linterp, it just requires an addition to the table at both sides you add a column with repeating values. See attached.

Success!
Luc

1_LM_20210429_Table_Interpolation.zip

F

Fred_Kohlhepp

23-Emerald I

Have a great care!

From your example there is a problem. There is a command (linterp) that will do what you ask, EXCEPT it will not extrapolate beyond the limits of your data. Your example has points beyond that range, and will require some thought.