Changes in version 2.0.4 (2024-08-21)                  

  - Fitted values and residuals have now the correct length even when
    there are zero weights.
  - Fixed a bug when calculating the variance for models with fixed
    parameters.
  - Function predict can now return standard errors and prediction
    intervals.
  - Upgraded Roxygen2 to version 7.3.2.

                 Changes in version 2.0.3 (2023-03-17)                  

  - Updated vignette after review from the Journal of Statistical
    Software.
  - Fixed again the x-axis of the plot.

                 Changes in version 2.0.2 (2022-11-25)                  

  - Fixed a bug in the plot when doses were not previously sorted.
  - Fixed a bug in the x-axis of the plot when data contained zeros.
  - It is now possible to not plot data points by setting option
    plot_data to FALSE (default TRUE).

                 Changes in version 2.0.1 (2022-07-08)                  

  - Small fixes to unit tests because they were not passing on specific
    systems.
  - Updated vignette with new simulation results.

                 Changes in version 2.0.0 (2022-06-17)                  

It is now possible to fit models using either the log-dose or the dose
scale.

To accommodate this extension it was necessary to change the default
model parameterization, which now follows that of the Emax model
(Macdougall, 2006).

Briefly, the 5-parameter logistic function is now defined as

alpha + delta / (1 + nu * exp(-eta * (x - phi)))^(1 / nu)

Parameter alpha is the value of the function when x approaches -Inf.
Parameter delta is the (signed) height of the curve. Parameter eta > 0
represents the steepness (growth rate) of the curve. Parameter phi is
related to the mid-value of the function. Parameter nu affects near
which asymptote maximum growth occurs.

Similarly, the newly implemented log-logistic function (when x >= 0) is
defined as

alpha + delta * (x^eta / (x^eta + nu * phi^eta))^(1 / nu)

Check the vignette (vignette("drda", package = "drda")) or the help page
(help(drda)) to know more about the available models.

Here is a change log from previous version:

  - Change parameterization to follow that of the Emax model.
  - Implement the log-logistic family of models.
  - Improve initialization algorithm to be more efficient and
    (hopefully) robust.
  - Exported functions for evaluating theoretical gradient and Hessian
    of each implemented model.
  - Implement the effective_dose function for estimating effective
    doses.
  - Added examples to help pages.
  - Many minor bug fixes (too many to list them all).

                 Changes in version 1.0.0 (2021-06-10)                  

First public release.