def scale_voltage_current_power(data, voltage=1, current=1):
    """
    Scales the voltage, current, and power of the DataFrames
    returned by :py:func:`singlediode` and :py:func:`sapm`.

    Parameters
    ----------
    data: DataFrame
        Must contain columns `'v_mp', 'v_oc', 'i_mp' ,'i_x', 'i_xx',
        'i_sc', 'p_mp'`.
    voltage: numeric, default 1
        The amount by which to multiply the voltages.
    current: numeric, default 1
        The amount by which to multiply the currents.

    Returns
    -------
    scaled_data: DataFrame
        A scaled copy of the input data.
        `'p_mp'` is scaled by `voltage * current`.
    """
    data = data.copy()
    voltages = ['v_mp', 'v_oc']
    currents = ['i_mp', 'i_x', 'i_xx', 'i_sc']
    data[voltages] *= voltage
    data[currents] *= current
    data['p_mp'] *= voltage * current
    return data
