<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def daily_plots( df, variable, renormalize = True, plot = True, scatter = False, linestyle = "-", linewidth = 1, s = 1 ):
 """ Create daily plots of a variable in a DataFrame, optionally renormalized. It is assumed that the DataFrame index is datetime. """

    if not df.index.dtype in ["datetime64[ns]", "<M8[ns]", ">M8[ns]"]:
        log.error("index is not datetime")
        return False
    days = []
    for group in df.groupby(df.index.day):
        days.append(group[1])
    scaler = MinMaxScaler()
    plt.xlabel("hours")
    plt.ylabel(variable);
    for day in days:
        if renormalize:
            values = scaler.fit_transform(day[[variable]])
        else:
            values = day[variable]
        if plot:
            plt.plot(day["hours_through_day"], values, linestyle = linestyle, linewidth = linewidth)
        if scatter:
            plt.scatter(day["hours_through_day"], values, s = s)