Numerical derivatives through finite-difference approximations
    can be calculated using the 'pnd' package with parallel capabilities and
    optimal step-size selection to improve accuracy. These functions facilitate
    efficient computation of derivatives, gradients, Jacobians, and Hessians,
    allowing for more evaluations to reduce the mathematical and machine errors.
    Designed for compatibility with the 'numDeriv' package,
    which has not received updates in several years, it introduces advanced features
    such as computing derivatives of arbitrary order, improving
    the accuracy of Hessian approximations by avoiding repeated differencing,
    and parallelising slow functions on Windows, Mac, and Linux.

Implements the methods for assessing heterogeneous cluster-specific treatment effects in partially nested designs as described in Liu (2024) <doi:10.1037/met0000723>. The estimation uses the multiply robust method, allowing for the use of machine learning methods in model estimation (e.g., random forest, neural network, and the super learner ensemble).  Partially nested designs (also known as partially clustered designs) are designs where individuals in the treatment arm are assigned to clusters (e.g., teachers, tutoring groups, therapists), whereas individuals in the control arm have no such clustering.

Provides tools for downloading, reading and analyzing the National
  Survey of Demographic and Health - PNDS, a household survey from Brazilian Institute
  of Geography and Statistics - IBGE. The data must be downloaded from the official
  website <https://www.ibge.gov.br/>. Further analysis must be made using package 'survey'.

This package provides an easy and simple way to read, write and display bitmap images stored in the PNG format. It can read and write both files and in-memory raw vectors.

Provides tools for downloading, reading and analyzing the National
  Survey of Health - PNS, a household survey from Brazilian Institute
  of Geography and Statistics - IBGE. The data must be downloaded from the official
  website <https://www.ibge.gov.br/>. Further analysis must be made using package 'survey'.