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Plot moderation curves with Johnson-Neyman highlights

Source: R/plot_moderation_curve.R
plot_moderation_curve.Rd

plot_moderation_curve() visualises how an indirect effect (theta_curve) or a path coefficient (path_curve) varies along a continuous moderator W.

The routine

  • extracts the requested record (path_name) from result$moderation, preferring theta_curve when it is available in both curves;

  • draws the conditional effect (Estimate) against the raw moderator grid (W_raw);

  • overlays the Monte-Carlo confidence band (CI.LL, CI.UL) and finds every Johnson–Neyman segment whose 95 % CI excludes zero (CI.LL * CI.UL > 0);

  • shades these significant regions and annotates each with its start / end percentiles (for example, "sig 12.5%-38.3%").

Visual elements

  • Red ribbon – overall 95 % confidence band (ns_fill);

  • Green ribbon – significant Johnson–Neyman intervals (sig_fill);

  • Solid line – point estimate;

  • Dashed h-line – zero reference;

  • Dashed v-lines – J–N bounds.

Usage

plot_moderation_curve(
  result,
  path_name,
  title = NULL,
  x_label = "Moderator (W)",
  y_label = "Estimate",
  ns_fill = "#FEE0D2",
  sig_fill = "#C7E9C0",
  alpha_ci = 0.35,
  alpha_sig = 0.35,
  base_size = 14
)

Arguments

result

A wsMed() result that contains a $moderation element.

path_name

Exact name of the path to plot (e.g. "indirect_1_2" or "b_1_2"). When the name exists in both curves, theta_curve is used.

title

Optional plot title (default sprintf("Effect Curve: (%s)", path_name)).

x_label, y_label

Axis labels. Defaults are "Moderator (W)" and "Estimate".

ns_fill, sig_fill

Fill colours for the confidence band and the significant regions.

alpha_ci, alpha_sig

Alpha values for the two ribbons.

base_size

Base font size passed to ggplot2::theme_minimal().

Value

A ggplot object (add layers or save with ggsave()).

Examples


data("example_data", package = "wsMed")
result <- wsMed(
                data = example_data,
                M_C1 = c("A1","B1","C1"),
                M_C2 = c("A2","B2","C2"),
                Y_C1 = "D1",
                Y_C2 = "D2",
                form = "CP",
                W      = "D3",
                W_type = "continuous",
                MP     = c("a1","b2","d1","cp","b_1_2","d_1_2"),
                )
plot_moderation_curve(result, "indirect_effect_1_2") # indirect

plot_moderation_curve(result, "b_1_2")               # direct path