def get_plot_data(df, feature):
    """Extracts the features from the dataframe

    Parameters
    ----------
    df : dataframe
        A pandas dataframe with all the basic features as columns
    feature : list
        A list constainig the expresssion we want to extract
        e.g. ['feature_1 + feature_2']

    Returns
    -------
    array
        An array of the feature constructedf from the dataframe
    """

    df.eval('result=' + feature, inplace=True)
    data = df['result'].values

    return data