Initialize data from a 2-D numpy matrix.

def __init_from_np2d(self, mat, params_str, ref_dataset):
        """Initialize data from a 2-D numpy matrix."""
        if len(mat.shape) != 2:
            raise ValueError('Input numpy.ndarray must be 2 dimensional')

        self.handle = ctypes.c_void_p()
        if mat.dtype == np.float32 or mat.dtype == np.float64:
            data = np.array(mat.reshape(mat.size), dtype=mat.dtype, copy=False)
        else:
            # change non-float data to float data, need to copy
            data = np.array(mat.reshape(mat.size), dtype=np.float32)

        ptr_data, type_ptr_data, _ = c_float_array(data)
        _safe_call(_LIB.LGBM_DatasetCreateFromMat(
            ptr_data,
            ctypes.c_int(type_ptr_data),
            ctypes.c_int(mat.shape[0]),
            ctypes.c_int(mat.shape[1]),
            ctypes.c_int(C_API_IS_ROW_MAJOR),
            c_str(params_str),
            ref_dataset,
            ctypes.byref(self.handle)))
        return self