extractFDAFeatures API

[berndbischl]

ok, one problem is that we would like to have that function "act" on a task.

but we also need a basic "workhorse". for this we need to act on data (and target, do we really need the target for anything?).

so the current API is good, but we need to document that one line in "data" is always one complete time series.

[berndbischl]

and really learn from the design in Impute.R and ImputeMethods.R to see how to delegate to specific algorithms, and how "reimpute" works during prediction time.

[pfistfl]

So, I worked on this since friday:

The code currently resides in the fda_pull1_task_featExtract branch.

It is mostly done similar to impute.R and imputeMethods.R

Current API:

  t = extractFDAFeatures(fuelSubset.task, 
     feat.methods = list("UVVIS" = extractFDAMean(),
                                    "NIR" = extractFDAFourier(trafo.coeff = "amplitude")))

It should return a Task, but I have not solved that yet.

It currently returns a list, where

• $data is a data.frame containing the transformed values for each functional feature
• $desc is a extractFDAFeatDesc containing a description Object for extraction in predict phase.

extractFDAFeatures can be called for a data.frame as well, then target, fd.features and fd.grids, usually contained in the TaskDeschave to be supplied as well.

For predict phase we can pass a Task and a extractFDAFeatDesc

  t2 = reExtractFDAFeatures(fuelSubset.task, t$desc)

Questions:

• Discuss function and object names!

• For extractFDAFeatures.Task and reExtractFDAFeatures.Task we want to return a Task. This can either be done by changing the data of the old task and removing the FDATask class or by constructing a new Task and passing on the neccessary TaskDesc values.

• What else needs to be changed, so resampling automatically works?

• We might want some way of appending extracted Features to a Task, for example if i want min, max, mean or Fourier amplitudeand phase I would have to somehow do it once for each Method and then changeData?

• Do we need a convertFDATaskToNormalTask? We could do this by simply wrapping around extractFDAFeatures.Task or do we want to rename the function?

@smilesun @lbeggel

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