Creates a copy of this tabarray in the form of a numpy ndarray.

        Useful if you want to do math on array elements, e.g. if you have a 
        subset of the columns that are all numerical, you can construct a 
        numerical matrix and do matrix operations.

def extract(self):
        """
        Creates a copy of this tabarray in the form of a numpy ndarray.

        Useful if you want to do math on array elements, e.g. if you have a 
        subset of the columns that are all numerical, you can construct a 
        numerical matrix and do matrix operations.

        """
        return np.vstack([self[r] for r in self.dtype.names]).T.squeeze()