Reduce package dependencies

[hadjipantelis]

For example: Within fitted.FPCA, Hmisc::approxExtrap(...) can probably be dropped in favour of stats::spline( method = "natural", ... ). The performance deterioration will probably be minimal but we will be able to drop the depend to Hmisc which is a big dependency. Similarly dependencies on pracma and/or MASS probably could be trimmed too.

[CrossD]

I agree with dropping redundant dependencies. We may port Hmisc::approxExtrap to fdapace instead of using spline smoothing for the sake of minimizing changes. pracma may also be dropped, but I think since everyone has MASS installed it should be less of concern.

[hadjipantelis]

Agreed. I am planning to make the replacement, check if we get too many unit-tests complaining and then potentially re-write if needed.

[ChingChuan-Chen]

I was working on matlab function interp in R.
I can contribute that code which is written in RcppArmadillo and verified. I think that it’s what you need.

You can find interp.cpp in url.
The test file is in here.

[hadjipantelis]

Hello ChingChuan, thanks for being interested to contribute to fdapace. fdapace doesn't depend on RccArmadillo so there is a bit of an issue of introducing a new dependency and potentially not dropping a single one. You are welcome to fork out fdapace and integrate your code, we will be happy to review the relevant pull request.