zscore诉minmax归一化，为什么它们的结果看起来相同

Question

我正在尝试使用两种不同的标准化方法minmax和zscore标准化我的时间序列，并比较结果。这是我的代码：

def scale_raw_data_zscore(raw_data):
    scaled_zscore = pd.DataFrame()
    idx = 514844
    values = raw_data.loc[idx]['d_column'].values
    values = values.reshape((len(values), 1))
    scaler = StandardScaler()
    scaler = scaler.fit(values)
    normalized = scaler.transform(values)
    normalized = normalized.reshape(normalized.shape[0])
    normalized = pd.DataFrame(normalized, index=raw_data.loc[idx].index, columns=raw_data.columns)
    scaled_zscore = scaled_zscore.append(normalized)
    return scaled_zscore

def scale_raw_data_minmax(raw_data):
    scaled_minmax = pd.DataFrame()
    idx = 514844
    values = raw_data.loc[idx]['d_column'].values
    values = values.reshape((len(values), 1))
    scaler = MinMaxScaler(feature_range=(0, 1))
    scaler = scaler.fit(values)
    normalized = scaler.transform(values)
    normalized = normalized.reshape(normalized.shape[0])
    normalized = pd.DataFrame(normalized, index=raw_data.loc[idx].index, columns=raw_data.columns)
    scaled_minmax = scaled_minmax.append(normalized)
    return scaled_minmax

def plot_data(raw_data, scaled_zscore, scaled_minmax):
    fig = pyplot.figure()
    idx = 514844
    ax1 = fig.add_subplot(311) 
    ax2 = fig.add_subplot(312) 
    ax3 = fig.add_subplot(313)
    raw_data.loc[idx].plot(kind='line', x='date', y='d_column', ax=ax1, title='ID: ' + str(idx), legend=False, figsize=(20, 5))
    scaled_zscore.reset_index(drop=True).plot(kind='line', y='d_column', ax=ax2, title='zscore', color='green', legend=False, figsize=(20, 5))
    scaled_minmax.reset_index(drop=True).plot(kind='line', y='d_column', ax=ax3, title='minmax', color='red', legend=False, figsize=(20, 5))
    pyplot.show()

scaled_zscore = scale_raw_data_zscore(raw_data)
scaled_minmax = scale_raw_data_minmax(raw_data)
plot_data(raw_data, scaled_zscore, scaled_minmax)

我正在添加结果图。为什么两种缩放方法的结果都完全相同？为什么它们与原始数据有不同的模式？