How can I insert the values contained in a field of a nested structure into the indexes of a matrix contained in another field whithout a looping

Hello,

I am performing a segment classification and thus get a class vector for each segment. The pixel ids are contained in a nested structure as following:

d.S(1) = 
       ids: [845x1 double]

I would like to put the values of the class vector into a matrix like

imC(d.S(:).ids) = class(:)

whithout looping.

Thanks a lot.

Guillaume