Line Chart
==========

A :doc:`Callable </Callables/Callable>` for generating a line chart.

Definition
----------

.. py:class:: controller.callable.outputter.LineChart(self, x: ColumnReference, y: ColumnReference, title: str, x_axis_name: str, y_axis_name: str)

    :callable name: ``line_chart``
    :callable type: :doc:`Outputter </Callables/Types/Outputter>`

    :param x: A column reference to find values for the x-axis. 
    :type x: ColumnReference
    :param y: A column reference to find values for the y-axis. 
    :type y: ColumnReference
    :param title: The title of the chart.
    :type title: str
    :param x_axis_name: The name of the x-axis.
    :type x_axis_name: str
    :param y_axis_name: The name of the y-axis.
    :type y_axis_name: str

Parameters
----------

.. py:attribute:: x

    A column reference to find values for the x-axis. 

    :type: ColumnReference
    :required: True
    :choices: All columns in the target DataFrame
    
.. py:attribute:: y

    A column reference to find values for the y-axis. 

    :type: ColumnReference
    :required: True
    :choices: All columns in the target DataFrame

.. py:attribute:: title

    The title of the chart.

    :type: str
    :required: True

.. py:attribute:: x_axis_name

    The name of the x-axis.

    :type: str
    :required: True

.. py:attribute:: y_axis_name

    The name of the y-axis.

    :type: str
    :required: True

Output
------

A DataFrame is returned where it contains two columns matching the output conventions of an Outputter.

- The ``data`` column contains the generated line chart in PNG format.
- The ``type`` column indicates the data type to be ``image/png``.

Example configuration
---------------------

.. code-block:: javascript

    {
        "name": "foo",
        "callable": "line_chart",
        "params": {
            "x": "$get_courses.courses.course_id",
            "y": "$final_exam_means.means",
            "title": "Final Exam Means",
            "x_axis_name": "Course ID",
            "y_axis_name": "Mean"
        }
    }