.. _scaling_robust_tan_scaler:

Robust Tan Scaler Transformation
================================

The **Robust Tan Scaler** (RTS) is a normalization technique designed for continuous variables with heavy-tailed or skewed distributions, where extreme outliers can otherwise dominate standard scaling or min–max normalization.

..  figure:: ../../images/robust_tan_scaler/image_intro.png
    :align: center
    :width: 100%

    Example of the RTS being applied to magnetic data dominated by large field values over a mineralized body.

In geoscience, datasets frequently contain anomalous values spanning several orders of magnitude, with a few extreme points masking subtler regional trends. For example, in magnetic data, highly magnetic geological formations can yield anomalies reaching thousands of nanoteslas (e.g., 1000-3000 nT), far exceeding the typical variations of tens to hundreds of nanoteslas found in surrounding areas. These extreme values may introduce instabilities in subsequent analyses and modeling processes. A plain min–max scaler would either compress most data into a tiny subrange or clip the tails entirely; a standard scaler can leave unbounded tails. The RTS gracefully compresses outliers toward the ends of the target interval, preserving continuity and order without harsh truncation.

The RTS applies a three‐stage, outlier-aware normalization to one or more numeric properties:

1. **Standardize** each property so that its values lie roughly in \[-π/2, +π/2\] (mean = 0, σ = π/2).
2. **Tan-suppress** the tails: values beyond ±π/2 are smoothly compressed toward ±π via a piecewise arctan function.
3. **Min–max** project the full range \[-π, +π\] into your desired window \[min_val, max_val\] (default \[0, 1\]).

Interface
---------

The general parameters for the Robust Tan Scaler are shown in the :ref:`figure below <rts_ui_general>`.

.. image:: ../../images/robust_tan_scaler/ui_general.png
   :name: rts_ui_general
   :align: center
   :width: 100%

The options are described as follows:

Object Selection
^^^^^^^^^^^^^^^^

* **Client**: The object containing the dataset to be transformed using the Robust Tan Scaler.
* **Properties**: One or more Float data properties to scale.
* **Property group** (optional): If you have already grouped several properties, you may enable this to pick the entire group.

Bound values
^^^^^^^^^^^^

* **Minimum**: Lower bound of the output range (min_val).
* **Maximum**: Upper bound of the output range (max_val).

Output names
^^^^^^^^^^^^

* **Property prefix**: Prefix added to each property name in the output group.
* **Property group name**: Name of the new HDF5 property group created to hold the scaled data.

Tutorial
^^^^^^^^

The following video presents a tutorial on how to use the Robust Tan Scaler
application.

#. Launch Geoscience ANALYST and open your .geoh5 project.
#. Navigate to **Geology** > **Robust Tan Scaler**.
#. In the dialog, pick your **Client** and **Properties** (or **Property group**).
#. (Optional) Adjust **Minimum** and **Maximum** for the target range.
#. (Optional) Adjust **Property prefix** or **Property group name**.
#. Click **OK** to close the dialog and run the application, or **Apply** to run the application and keep the dialog open for further adjustments.
#. Inspect the transformed data.

.. figure:: ../../images/robust_tan_scaler/rts_tutorial.gif
   :name: rts_tutorial
   :align: center
   :width: 100%