def _standardize(dataframe):
    """Transform features by centering the distribution of the data
    on the value 0 and the standard deviation to the value 1.

    The transformation is given by:

        scaled_value = (value - mean) / standard deviation

    Parameters
    ----------
    dataframe : pandas.DataFrame
        The data frame to be used for EDA.
    Returns
    -------
    res : pandas.core.frame.DataFrame
        Scaled dataset
    """

    res = dataframe.copy()
    for feature_name in dataframe.columns:
        mean = dataframe[feature_name].mean()
        stdev = dataframe[feature_name].std()
        res[feature_name] = (dataframe[feature_name] - mean) / stdev
    return res