.. _auto_dataset_add_column_by_expression:

*ADD COLUMN BY EXPRESSION*
==========================

Appends a new computed column to a dataset by evaluating a user-supplied expression against existing columns. Use this worker when you need to derive a calculated field (e.g., unit conversions, arithmetic combinations, conditional logic) inline within a workflow without writing custom code.

When to use
-----------

Classification: **process**.

Tagged: ``column``, ``dataset``, ``derived_field``, ``expression``, ``process``, ``transform``.

Inputs
------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20 20 20

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Dataset
     - dataset
     - dataset
     - —
     - 
     - Input dataset (tabular) to which the new computed column will be appended; accepts any d3VIEW dataset object passed from an upstream worker.
   * - New Column name
     - new_columnname
     - text
     - —
     - 
     - Name of the new column to create; must be a valid string identifier that does not conflict with existing column names in the dataset.
   * - Expression
     - expression
     - text
     - —
     - 
     - Mathematical or logical expression (e.g., 'col_a * 2 + col_b') evaluated row-wise to produce values for the new column; reference existing column names as variables.

Outputs
-------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20

   * - Label
     - ID
     - Type
     - Description
   * - dataset_add_column_by_expression_output_1
     - dataset_add_column_by_expression_output_1
     - dataset
     - A copy of the input dataset with the newly computed column appended as the last column, preserving all original rows and columns.

Disciplines
-----------

- data.dataset.transform

Runnable example
----------------

A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: `/api/workflow/example?id=dataset_add_column_by_expression <https://www.d3view.com/api/workflow/example?id=dataset_add_column_by_expression>`_

.. raw:: html

   <hr style="margin-top:2em">
   <p style="font-size:11px;color:#888">
   Auto-generated from <code>transformation</code> schema. Worker id: <code>dataset_add_column_by_expression</code>. Schema hash: <code>53cca26c82a1</code>. Hand-curated docs in <code>workerexamples/</code> override this page when present.
   </p>