Adding Extrapolation feature into Interpolation function

Questions
,
1

Hi all,
I have created a simple Interpolation[] function and I would like to ask if it is possible to set some extrapolation method.
Thank you
Paolo

2

You could try to create (from your data) the next models:
LinearModelFit
NonlinearModelFit
etc.,
they are suitable for extrapolation.
But it’s better if you post your code and sample data, then we can find a solution.

3

You can set an arbitrary function to handle extrapolation:

ifn = Interpolation[Range[10]^2,
  "ExtrapolationHandler" -> {
    Piecewise[{{100 - (# - 10)^2, x >= 10}}, 1 + 10 (1 - #)] &, 
    "WarningMessage" -> False
    }]

If you want extrapolation to be undefined, do something like this:

ifn = Interpolation[Range[10]^2,
  "ExtrapolationHandler" -> {
    Indeterminate &,
    "WarningMessage" -> False
    }]

Of course, Denis’s suggestions are better if you have a model for your data.