NRW.42 Dataset
=============

Description
-----------

* Target Soil Properties: SOC, pH, Clay
* Groups of Features: MIR 
* Sample size: 42
* Number of Features: 1,686
* Coordinates: Without coordinates because of privacy concerns
* Location: North Rhine-Westphalia, Germany
* Sampling Design: Regular grid sampling
* Study Area Size: 1.5 ha
* Geological Setting: Pleistocene periglacial slope deposits consisting of weathered Devonian sand-, silt-, and claystones, partially covered by Weichselian loess
* Previous Data Publication: None
* Contact Information:
    * Stefan Paetzold (s.paetzold@uni-bonn.de), University of Bonn
* License: CC BY-SA 4.0
* Publication/Modification Date (d/m/y): 28.02.25, version 1.0
* Changelog:
    * Version 1.0 (28.02.25): Initial release

Details
-------

Dataset
^^^^^^^
The dataset contains the following target soil properties and features:

Target Soil Properties:
""""""""""""""""""""""

SOC - Soil Organic Carbon
    * Code: ``SOC_target``
    * Unit: %
    * Protocol: Determined by the difference of total carbon and inorganic carbon, where total carbon was obtained through elemental analysis by measuring the CO₂ release during dry combustion (DIN ISO 10694) without acid pretreatment and inorganic carbon as 0.12 x the calcium carbonate content, determined by the gas-volumetric Scheibler Method (ISO 10693)
    * Sampling Date: April 2013
    * Sampling Depth: 0 - 30 cm

pH
    * Code: ``pH_target``
    * Unit: Unitless
    * Protocol: Measured in CaCl₂ suspension with a glass electrode with a 5:1 liquid:soil volumetric ratio (DIN ISO 10390)
    * Sampling Date: April 2013
    * Sampling Depth: 0 - 30 cm

Clay
    * Code: ``Clay_target``
    * Unit: %
    * Protocol: Sieve-Pipette method, measured through fractioning the soil into the sand fractions by sieving, and the silt and clay fractions by sedimentation in water, German adaptation (DIN ISO 11277)
    * Sampling Date: April 2013
    * Sampling Depth: 0 - 30 cm

Groups of Features:
"""""""""""""""""

MIR – Mid Infrared Spectroscopy
    * Number of Features: 1,686
    * Code(s): ``wn_3799``, ``wn_3797.1``, ``wn_3795.1`` ... ``wn_549.6``
    * Unit: % (Reflectance)
    * Sensing: MIR spectrometer (Bruker Tensor 27 HTS-XT, Bruker Optik, Ettlingen, Germany), on dried and sieved samples (<2 mm) in the laboratory, spectral range was 7,500 – 550 cm⁻¹ at 4 cm⁻¹ intervals
    * Processing: Discarding irrelevant spectral data of the spectrum (7,500 - 3,799 cm⁻¹), resampling to ~2 cm⁻¹ intervals
    * Sampling Date: April 2013
    * Spectral Information (After Data Processing):
        * Data Representation: Wavenumber (in cm⁻¹)
        * Spectral Resolution: ~2 cm⁻¹
        * Spectral Range: 3,799 - 549.6 cm⁻¹

Examples
--------

.. code-block:: python

    from LimeSoDa import load_dataset, split_dataset
    from sklearn.linear_model import LinearRegression
    from sklearn.metrics import r2_score, mean_squared_error
    import numpy as np

    # Load and explore the dataset
    data = load_dataset("NRW.42")
    dataset = data["Dataset"]
    folds = data["Folds"]
    coords = data["Coordinates"]  # Will be NA for NRW.42

    # Split into train/test using fold 1
    X_train, X_test, y_train, y_test = split_dataset(
        data=data,
        fold=1,
        targets=["pH_target", "SOC_target", "Clay_target"]
    )

    # Fit model and get predictions
    model = LinearRegression()
    model.fit(X_train, y_train)
    predictions = model.predict(X_test)

    # Calculate performance metrics
    r2 = r2_score(y_test, predictions)
    rmse = np.sqrt(mean_squared_error(y_test, predictions))
    print(f"R-squared: {r2:.7f}")
    print(f"RMSE: {rmse:.7f}")

References
----------

Gee, G.W. & Bauder, J.W. (1986) Particle-Size Analysis. In: Klute, A., Ed., Methods of Soil Analysis, Part 1. Physical and Mineralogical Methods, Agronomy Monograph No. 9, 2nd Edition, American Society of Agronomy/Soil Science Society of America, Madison, WI, 383-411.

Walkley, A. & Black, I. A. (1934). An examination of the Degtjareff method for determining soil organic matter, and a proposed modification of the chromic acid titration method. Soil science, 37(1), 29-38.