Provides access to granular sub-national income data from the
    MCC-PIK Database Of Sub-national Economic Output (DOSE). The package
    downloads and processes the data from its open repository on 'Zenodo'
    (<https://zenodo.org/records/13773040>). Functions are provided to
    fetch data at multiple geographic levels, match coordinates to
    administrative regions, and access associated geometries.

Effect modification occurs if a treatment effect is larger or more stable in certain subgroups defined by observed covariates.  The submax or subgroup-maximum method of Lee et al. (2018) <doi:10.1111/biom.12884> does an overall test and separate tests in subgroups, correcting for multiple testing using the joint distribution.

The subplex algorithm for unconstrained optimization, developed by Tom Rowan.

Estimation of copula using ranks and subsampling. The main feature of this method is that simulation studies show a low sensitivity to dimension, on realistic cases.

Balancing computational and statistical efficiency, subsampling techniques offer
    a practical solution for handling large-scale data analysis. Subsampling methods
    enhance statistical modeling for massive datasets by efficiently drawing
    representative subsamples from full dataset based on tailored sampling probabilities. These
    probabilities are optimized for specific goals, such as minimizing the variance
    of coefficient estimates or reducing prediction error.

Functions for computing test subscores using different
    methods in both classical test theory (CTT) and item response theory (IRT). This
    package enables three types of subscoring methods within the framework of CTT
    and IRT, including (1) Wainer's augmentation method (Wainer et. al., 2001) 
    <doi:10.4324/9781410604729>, (2) Haberman's subscoring methods (Haberman, 2008) 
    <doi:10.3102/1076998607302636>, and (3) Yen's objective performance index (OPI; Yen, 1987) 
    <https://www.ets.org/research/policy_research_reports/publications/paper/1987/hrap>. 
    It also includes functions to compute Proportional Reduction 
    of Mean Squared Errors (PRMSEs) in Haberman's methods which are used to 
    examine whether test subscores are of added value. In addition, the package includes 
    a function to assess the local independence assumption of IRT with
    Yen's Q3 statistic (Yen, 1984 <doi:10.1177/014662168400800201>; Yen, 1993 
    <doi:10.1111/j.1745-3984.1993.tb00423.x>).