Replacement (?) for `scipy.interpolate.interp1d`

[qian-chu]

scipy.interpolate.interp1d is a legacy (but not deprecated) function, but it offers simplicity in API that average users might enjoy.

Possible solutions:

• Keep the current implementation using the class, but keep an eye on the Scipy documents
• Keep a interp1d-like API, but call specialized interpolators as mentioned in https://scipy.github.io/devdocs/tutorial/interpolate/1D.html#legacy-interface-for-1-d-interpolation-interp1d
• Ask users to supply callable interpolators (which is not that user-friendly)