Implements choice models based on economic theory, including
    estimation using Markov chain Monte Carlo (MCMC), prediction, and
    more. Its usability is inspired by ideas from 'tidyverse'. Models
    include versions of the Hierarchical Multinomial Logit and Multiple
    Discrete-Continous (Volumetric) models with and without screening. The
    foundations of these models are described in Allenby, Hardt and Rossi
    (2019) <doi:10.1016/bs.hem.2019.04.002>. Models with conjunctive
    screening are described in Kim, Hardt, Kim and Allenby (2022)
    <doi:10.1016/j.ijresmar.2022.04.001>. Models with set-size variation
    are described in Hardt and Kurz (2020) <doi:10.2139/ssrn.3418383>.

An R interface to United States Environmental 
    Protection Agency (EPA) Environmental Compliance 
    History Online ('ECHO') Application Program Interface
    (API). 'ECHO' provides information about EPA permitted 
    facilities, discharges, and other reporting info 
    associated with permitted entities. Data are obtained 
    from <https://echo.epa.gov/>.

Provides a lightweight implementation of functions and methods for
    fast and fully automatic time series modeling and forecasting using Echo
    State Networks (ESNs).

Extends the Changes-in-Changes model a la Athey and Imbens
    (2006) <doi:10.1111/j.1468-0262.2006.00668.x> to multiple cohorts and
    time periods, which generalizes difference-in-differences estimation
    techniques to the entire distribution. Computes quantile treatment
    effects for every possible two-by-two combination in ecic(). Then,
    aggregating all bootstrap runs adds the standard errors in
    summary_ecic(). Results can be plotted with plot_ecic() aggregated
    over all cohort-group combinations or in an event-study style for
    either individual periods or individual quantiles.

Provides a function that quickly computes the fine structure
    isotope patterns of a set of chemical formulas to a given degree of
    accuracy (up to the limit set by errors in floating point arithmetic). A
    data-set comprising the masses and isotopic abundances of individual
    elements is also provided and calculation of isotopic gross structures
    is also supported.