Extractors

[arushanova]

I'm going to use the limit setting part of echidna to look at how the pileup rejection helps improving the limit of 0nu. At the moment in order to create a spectra class I have to prepare the root file (i.e. apply the pileup cuts) first and then just to fill in an empty spectra with the energies. This leads to the question if we want to add more extractors? I've written the options I can see and comments below.

1) We will add more extractors. This extractors will be basically representing the cuts. I personally will need to implement about five extractors, that are the classifiers I use for cuts.

• The extractors then should be dependent on the input, so that a person will choose which extractor (i.e. cut) values he wants to apply.
• The good thing about this is that the cut value can be one of the fitting parameter.
• The negative thing is that do we actually need this?

2) We are not adding more extractors. It is quite simple for a user to keep the code that prepares the pdf personal. In this case a person can apply any cuts before he turns his file into a spectra class.

• First of all, this won't make an impression that creating a spectra is hardcoded. On contrary a simple example and recommendations will allow freedom at this step.
• A lot of extractors shouldn't be included into echidna, because they have the only purpose - creating a spectra. And they can be easily used in outside of echidna.
• ds structure might change again and this won't affect echidna.
• if a person want to implement cut as one of the parameter he can add extractor if he wants to.

[jwaterfield]

@arushanova I think its always useful to add a new extractor to echidna if you have written it and is not there already. Mainly because there is no way of knowing whether people will use it in the future even if you are the only one using it currently and a pull request means that your code will be checked by another person which will minimise the risk of any bugs in your analysis code. Plus everyone can pick and choose whatever extractors they want to use so if they dont want to use your one then they dont have to and it wont effect their spectra or how echidna interacts with the spectra (or echidnas speed) but if the extractor is in the main code then at the very least the person has the option to choose to use it which they wouldnt have if it werent in the main code.

[ashleyrback]

@arushanova does @mjmottram's #129 help here?