Air pollution tutorial should show path to "vectorization"

The air polution tutorial has a "vectorized" function to calculte the AIQ (IIRC). This can be vectorized using searchsorted (which is a bit much work, but not too tricky).
I am also almost completely certain that it can also be replaced with a single call to np.interp1d.

Having the "vectorize" version seems good, but doesn't fully leverage the concepts that NumPy provides. I think it would be great arc to keep it, but then also show the final interp and maybe even the searchsorted idea. (I honestly don't like stopping at vectorize becuzse it makes seems that vectorize is a common approach, when I consider it more of a fallback solution – whether used a lot in practice or not.)

Inizia dal tutorial sull’inquinamento atmosferico e individua la funzione vettorializzata esistente utilizzata per calcolare l’AQI. Confronta come il tutorial potrebbe presentare l’approccio vectorize insieme alle idee di searchsorted e interpolazione; il lavoro è completato quando il tutorial spiega queste alternative e non lascia intendere che vectorize sia l’unico percorso.