<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_data_values(self, label, x, y, z):
 """ Set the position of the datapoints """

        # TODO: avoid re-allocating an array every time
        self.layers[label]['data'] = np.array([x, y, z]).transpose()
        self._update()