def dropdown_options(radio_value):
    """
    This function will base on the radio value to allows the dropdown menu to have certain value

    param radio_value: a string either 'bar' or 'scatter'
    return: an option for the dropbar menu, and the default value
    """
    # if the radio value is bar then the value can be 'Price', 'Area', 'Length', and 'Width'
    if radio_value == 'bar':
        options = [{'label': x, 'value': x} for x in ['Price', 'Area', 'Length', 'Width']]
        # set the default value as 'Price'
        value = 'Price'
    # if the radio value is scatter then the value will be exclude the 'Price' compare to the bar option
    else:
        options = [{'label': x, 'value': x} for x in ['Area', 'Length', 'Width']]
        # set the default value as 'Area'
        value = 'Area'
    # return the list of option and the default value
    return options, value