Utility Functions for Davidian Curves

A Davidian curve defines a seminonparametric density, whose shape and flexibility can be tuned by easy to estimate parameters. Since a special case of a Davidian curve is the standard normal density, Davidian curves can be used for relaxing normality assumption in statistical applications (Zhang & Davidian, 2001) . This package provides the density function, the gradient of the loglikelihood and a random generator for Davidian curves.


Davidian curves in R

A Davidian curve defines a seminonparametric density, whose shape and flexibility can be tuned by easy to estimate parameters. Since a special case of a Davidian curve is the standard normal density, Davidian curves can be used for relaxing normality assumption in statistical applications [1].

This package provides the density function, the gradient of the loglikelihood and a random generator for Davidian curves:

  1. ddc(x, phi), Davidian curve density function
  2. rdc(n, phi), a random sampler for Davidian curves
  3. dc_grad(x, phi), the gradient function of Davidian curves

The second argument phi of these functions is a vector, which contains the parameter(s) of a Davidian curve. The higher the number of parameters, the more flexible the density. The values of the parameres define the shape of the curve. Following [1, 2], this package provides support for Davidian curves up to 10 parameters.

References

  1. Zhang, D., & Davidian, M. (2001). Linear mixed models with flexible distributions of random effects for longitudinal data. Biometrics, 57(3), 795-802.
  2. Woods, C. M., & Lin, N. (2009). Item response theory with estimation of the latent density using Davidian curves. Applied Psychological Measurement, 33(2), 102-117.

News

News

v0.9.1

  • Approximate values in M matrix are replaced with analytically obtained values (#9). Relevant code is reorganized.
  • Bounds for Davidian curve parameters are removed. Thanks to R. Philip Chalmers for suggestions on this point.

v0.9.0

  • Initial release.
  • Thanks to Carol M. Woods for kindly answering my questions prior to this release.

Reference manual

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install.packages("dcurver")

0.9.1 by Oğuzhan Öğreden, a year ago


https://github.com/oguzhanogreden/dcurver


Report a bug at https://github.com/oguzhanogreden/dcurver/issues


Browse source code at https://github.com/cran/dcurver


Authors: Oğuzhan Öğreden


Documentation:   PDF Manual  


GPL-3 license


Imports Rcpp

Suggests testthat

Linking to Rcpp, RcppArmadillo


Imported by mirt.


See at CRAN