Derivative-parameters as output of `obic_field()`

[JobdePater]

If output type 'all' is choosen the calculated derivatives (*D-parameters, eg D_SLV or D_PBI) are not in the output.

This might be a welcome addition to get quick insight of the field characteristics (what causes a low or high score?).

[SvenVw]

Hmm, I think output should be limited to only scores and indicators. Internal parameters can always be calculated with the individual functions if one is interested. Type is all means that the indicators are also returned instead of only the scores.

[JobdePater]

But to prevent extra work (typing all separate functions) it might be helpful. Other options might be:

• add type is derivatives
• add function obic_derivatives()