Package: tppcm
Type: Package
Title: Step Discriminations for the Two-Parameter Partial Credit Model
        on Top of 'TAM'
Version: 0.1.0
Authors@R: person("Jie-Wen", "Tsai", email = "tsai.jiewen@gmail.com", role = c("aut", "cre"))
Description: In the two-parameter partial credit model (TPPCM) of Yu
        (1991) <https://hdl.handle.net/2142/21459>, every step of a
        polytomous item has its own discrimination. Estimation is left
        to existing software: 'TAM' (tam.mml.3pl() with a step design
        matrix, tam.mml.2pl(), tam.mml()) and, for the bilinear product
        form and non-negativity constraints, 'sirt' (xxirt()). The
        package adds what these packages do not provide: standard
        errors of step discriminations based on the full observed
        information, step-level Wald tests, and score tests with
        modification indices and expected parameter changes for moving
        down the model ladder saturated TPPCM -> product form ->
        generalized partial credit model -> partial credit model,
        limited-information fit statistics (the M2 statistic, root mean
        square error of approximation, standardized root mean squared
        residual, comparative fit index and Tucker-Lewis index;
        Maydeu-Olivares and Joe (2006) <doi:10.1007/s11336-005-1295-9>)
        for any step design, step contributions to the item
        information, and tests of differential step functioning across
        groups: per-step Lagrange multiplier tests from one multigroup
        fit (Glas (1998)
        <https://www3.stat.sinica.edu.tw/statistica/j8n3/j8n32/j8n32.htm>),
        with the generalized score test of Boos (1992)
        <doi:10.1080/00031305.1992.10475921>, likelihood ratio tests
        with configural, metric, scalar and partial multigroup designs,
        score-based tests (Merkle and Zeileis (2013)
        <doi:10.1007/s11336-012-9302-4>) and model-based trees
        (Zeileis, Hothorn and Hornik (2008)
        <doi:10.1198/106186008X319331>). The generalized partial credit
        model of Muraki (1992) <doi:10.1177/014662169201600206> is the
        special case with equal steps within items.
License: GPL (>= 2)
URL: https://github.com/jiewenTsai/tppcm
BugReports: https://github.com/jiewenTsai/tppcm/issues
Encoding: UTF-8
Language: en-US
Depends: R (>= 4.1), TAM
Imports: CDM, graphics, MASS, sirt, stats
Suggests: knitr, mirt, numDeriv, partykit, psychotools, psychotree,
        rmarkdown, strucchange, testthat (>= 3.0.0)
VignetteBuilder: knitr
Config/testthat/edition: 3
RoxygenNote: 7.3.2
NeedsCompilation: no
Packaged: 2026-10-28 20:00:05 UTC; root
Author: Jie-Wen Tsai [aut, cre]
Maintainer: Jie-Wen Tsai <tsai.jiewen@gmail.com>
Repository: https://cran.r-universe.dev
Date/Publication: 2026-10-28 11:00:02 UTC
RemoteUrl: https://github.com/cran/tppcm
RemoteRef: HEAD
RemoteSha: 1168ea62adf7b6f76bc8368ac5d0188b721f9347