To be more precise: Modin’s definition of a dataframe is a 4-tuple (A_mn, S_n, C_n, R_m) where S_n is a collection of schema induction functions (parsing function) from String to a Type. The underlying 2D array can be transposed. This would invalidate S_n so it would have to be regenerated or initialized as a list of identity functions. Of course this is only a theoretical definition that’s almost impossible to implement efficiently. And I admit it does seem very post hoc but dataframes are weird…
Speaking to a lot of people that use dataframes as a way to clean data (as opposed to a query engine) this sort of operation is useful. And I think the example in the Modin paper is illustrative of an intuitive use of transposition.