def to_numpy(self):
        """
        Converts this SFrame to a numpy array

        This operation will construct a numpy array in memory. Care must
        be taken when size of the returned object is big.

        Returns
        -------
        out : numpy.ndarray
            A Numpy Array containing all the values of the SFrame

        """
        assert HAS_NUMPY, 'numpy is not installed.'
        import numpy
        return numpy.transpose(numpy.asarray([self[x] for x in self.column_names()]))