handle n = 1

[andrewGhazi]

A few tweaks to prevent R from dropping dimensions and erroring out when n = 1 i.e.

Stool_simulation <- SparseDOSSA2(template = "Stool", 
                                 new_features = TRUE,  
                                 n_sample = 1, 
                                 n_feature = 100, 
                                 verbose = TRUE)

will run.