Adding Smoothstep function and Blendable interface to Hipparchus

Hi everyone,

I’m currently working on state covariance interpolation and now trying to implement it in Orekit.

However, a small part of what I am doing should be in Hipparchus rather than Orekit :

  • Implementation of smoothstep function as explained here (generalized formula for smoothstep function of order N right below the middle of the page).

  • Implementation of a Blendable interface defining a “blendWith” method for example. This follows the concept of blending exposed in “Efficient Covariance Interpolation using Blending of Approximate State Error Transitions” by Sergei Tanygin. This “blendWith” method would define how to blend Vector3D or RealMatrix for example, using a chosen smoothstep function.

What do you think ?

Good idea.

Thank you @luc !

I’ll create an issue about it and then propose a merge request.