Fix in Start() to work with sub_array_indices

Hi @aho,

This merge request fixes issue #38 (closed).

I think you should review it, so, you can keep track of all the modifications undertaken in the package.

On the other hand, do you have any way to automatically tests that check the modifications done in the code to not break the function? I think you should prepare automatic tests for startR as you already did for some functions in s2dverification using testthat. In this case, you can use the examples from "use cases" documentation as starting point.

Thanks,

Núria