functions for linear and cubic spline interpolation in Calc?

How can I make linear and cubic spline interpolations by using formulas? Libreoffice can draw interpolated lines using both of these interpolations if I make a graph, but how can I make the interpolation directly into a table?

So far I haven’t been able to locate any plugins of funtions that can solve this.

Example, linear:
x1=10, x2=20, y1=30, y2=50

CALCULATE: y for x=15

Example, spline:
x1=10, x2=20, x3=30, y1=100, y2=400, y3=900

CALCULATE: y for x=13

There is a plugin for Microsoft Excel that does the trick here, but thats no good for Libreoffice.

Linear interpolation is used all over, and cubic spline is state of the art interpolation used in stuff as engineering an rocket science :slight_smile:

There is no built-in function equivalent for LO. The AOO forum thread here offers an example of a spline using a macro, which is likely the method that needs to be considered.

Hi, it is an old question, nevertheless, Why don’t you try this one. also found here?
Let me know how it was

kind regards

You may try this one:

kinds regards