5.25. Plugins: Write your own data processing code

5.25.1. Example: A Predictive Model

Suppose that your favorite data analyst has processed the data set and created a predictive model that estimates the score of the final exam based on the value of the column Contributions applying the following linear equation:

final exam score = 3.73 * Contributions + 25.4

You would like to incorporate this model to the workflow and use the predicted final exam score as another column to create conditions and personalize content. One way to achieve this is by creating a plugin that given the two coefficients of a linear model (in the example 3.73 and 25.4) returns a new data set with a column with the values obtained using the corresponding equation. In order for the plugin to comply with the requirements, one possible definition would be:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals, print_function

import pandas as pd

# The field class_name contains the name of the class to load to execute the
# plugin.
class_name = 'OnTaskTestPlugin'


class OnTaskTestPlugin:
    """
    Example of a class that implements the OnTask plugin interface. The
    objects of this class have to provide the following elements:

    1. name: Plugin name show to the users.

    2. description_txt: A string with the detailed description of what the
    plugin does

    3. input_column_names: A potentially empty list of column names (strings).
    If the list is empty, the columns are selected by the user at execution
    time.

    4. output_column_names: Non empty list of names (strings) of the columns
    to be used for the output of the transformation.

    5. parameters: an optionally empty list with tuples with the following
      structure:

      ('name', type, [list of allowed values], initial value, help_text)

      These elements will be requested from the user before executing the
      plugin through a form. The conditions on these values are:

      - name must be a string
      - type must be a string equal to "integer", "double", "string",
        "datetime" or "boolean".
      - The list of values is to restrict the
        possible values
      - The initial value must be of the type specified by the second
        element.
      - Help_text a string to show as help text

    6. method "run" that receives:
       - a pandas data frame with the data to process
       - a string with the name of the key column that will be used to merge
       the result.
       - A dictionary of pairs (name, value) with the parameters described in
       the previous element.

       and returns a result Pandas data frame. This frame **must** have one
       column with the key column name provided so that it can be properly
       merged with the existing data.
    """

    def __init__(self):
        self.name = 'Test Plugin 1 Name'
        self.description_txt = 'Test Plugin 1 Description Text'
        self.input_column_names = list()
        self.output_column_names = ['RESULT 1', 'RESULT 2']
        self.parameters = [
            ('param string', 'string', ['v1', 'v2'], 'v1', 'help param string'),
            ('param integer', 'integer', [], None, 'help param integer'),
            ('param double',
             'double',
             [1.2, 2.2, 3.2],
             None,
             'help param double'),
            ('param boolean', 'boolean', [], True, 'help param boolean'),
            ('param datetime',
             'datetime',
             [],
             '2018-05-25 18:03:00+09:30',
             'help param datetime'),
            ('param datetime2',
             'datetime',
             [],
             '2018-05-25 18:03:00+09:30',
             'help param datetime'),
        ]

    def run(self, data_frame, merge_key, parameters=dict):
        """
        Method to overwrite. Receives a data frame wih a number of columns
        stipulated by the num_column_input pair, the name of a key column and a
        dictionary with parameters of the form name, value.

        Runs the algorithm and returns a pandas data frame structure that is
        merged with the existing data frame in the workflow using the merge_key.

        :param data_frame: Input data for the plugin
        :param merge_key: Name of the column key that will be used for merging
        :param parameters: Dictionary with (name, value) pairs.

        :return: a Pandas data_frame to merge with the existing one (must
        contain a column with name merge_key)
        """

        # Extract the key column from the given data frame
        result = pd.DataFrame(data_frame[merge_key])

        # Process the given data and create the result
        result[self.output_column_names[0]] = 1
        result[self.output_column_names[1]] = 2

        return result