Changes in version 0.2.0 (2026-04-16)                  

Major new features

  - Two-way and nested clustering via cluster = c("g1","g2") and nested
    = TRUE/FALSE, generating (1|g1/g2) or (1|g1) + (1|g2) random-effects
    structures in lme4.

  - Automatic knot / df selection (df = "auto" in nl_fit() or via
    nl_knots()) using AIC or BIC over a user-specified grid.

  - Multilevel R-squared decomposition (nl_r2()): Nakagawa-Schielzeth
    marginal R2m and conditional R2c, plus a level-specific variance
    partition table (r2_mlm style) for LMM, GLMM, and single-level OLS /
    GAM models.

  - Full postestimation suite:
    
      - nl_derivatives() — first and second derivatives with
        delta-method confidence bands.
      - nl_turning_points() — local maxima, minima, inflection regions,
        and slope-direction regions.
      - nl_plot() gains type = "slope", "curvature", and "combo" in
        addition to the original "trajectory".

  - Built-in model comparison workflow (nl_compare()): contrasts linear,
    polynomial, and spline fits by AIC, BIC, log-likelihood, and
    likelihood-ratio tests.

  - B-spline basis (method = "bs", bs_degree argument).

  - Random spline slopes (random_slope = TRUE) to allow the nonlinear
    effect to vary across clusters.

  - Cluster heterogeneity analysis (nl_het()): plots cluster-specific
    trajectories (BLUPs) and performs an LRT comparing random-slope vs
    random-intercept models.

  - CI for glmerMod: approximate confidence intervals via the delta
    method on the link scale (default, fast) or parametric bootstrap
    (glmer_ci = "boot").

Breaking changes

None. All v0.1.0 calls remain valid.

Bug fixes

  - nl_r2() variance partition now correctly excludes NA entries that
    could appear when lme4 internal row names are ambiguous in nested
    models.
  - nl_predict() now correctly computes CI when control variables are
    stored as character (not factor) in the original data.
  - nl_plot() no longer errors when time = NULL and the data frame has
    no time column.

Dependency changes

  - %||% is now imported from rlang rather than defined internally,
    avoiding namespace masking.
  - reformulas moved from Imports to Suggests (used opportunistically
    for nobars(); falls back to lme4::nobars() if unavailable).

                        Changes in version 0.1.0                        

  - Initial release: nl_fit(), nl_predict(), nl_plot(), nl_summary(),
    nl_icc().