Plot the floor-group additive model against the data — plot_floor

Visualises a floor-group additive model's key claim: a single continuous relationship among above-floor participants, with the complete-aphantasia (floor) group's actual mean shown alongside where that relationship, extrapolated to VVIQ=16, would have predicted it — making the model's central coefficient (the floor-group shift) a visible gap rather than an abstract number. Works with any outcome variable (total TAS-20 score or any of its subscales) — the outcome column is read directly from the fitted model object, not hardcoded, so the same function call pattern applies whether model was fit on tas, tas_identify, tas_describe, or tas_external.

Usage

plot_floor_group(
  model,
  data,
  x_lab = "VVIQ score",
  y_lab = "Total TAS score",
  limits = c(8, 81),
  vviq_breaks = seq(16, 80, 4),
  tas_breaks = seq(20, 100, 20),
  dot_size = 1.2,
  dot_alpha = 0.4,
  cross_size = 2,
  cross_stroke = 0.8,
  violin_width = 3,
  stat_txt_size = 1.75,
  xbar_label = "Sample\nmean",
  xbar_face = "italic",
  xbar_vjust = 0.5,
  colorbar_width = 14,
  mean_line_color = "grey40",
  mean_line_width = 0.2,
  floor_fill_color = "#C44E52",
  floor_line_color = "#8B3A3E",
  floor_violin_alpha = 0.6,
  floor_violin_linewidth = 0.2,
  floor_violin_nudge = -2,
  floor_jitter_alpha = 0.2,
  floor_jitter_size = 1.2,
  floor_pointrange_linewidth = 0.5,
  floor_pointrange_size = 0.4,
  floor_guide_color = "grey82",
  floor_guide_linewidth = 0.2,
  floor_guide_y_pad = 5,
  floor_label_x = 15.2,
  floor_label_y = 20,
  floor_label_color = "grey65",
  floor_label_size = 1.75,
  arrow_x = 10.5,
  arrow_linewidth = 0.3,
  arrow_length = 0.05,
  tick_linewidth = 0.2,
  stat_label_x = 8.2,
  stat_label_lineheight = 0.9,
  fitted_line_color = "black",
  fitted_line_width = 0.5,
  extrap_line_width = 0.4,
  base_theme = ggplot2::theme_minimal,
  axis_relative_size = 0.85,
  axis_relative_x = 1,
  axis_relative_y = 1,
  ...
)

Arguments

model: A fitted brms model from a formula of the form <outcome> ~ vviq + complete_aphant or <outcome> ~ vviq + complete_aphant + (vviq | study) — single- or multi-level both work, thanks to re_formula = NA on the internal prediction calls.
data: The data frame the model was fit on (must contain vviq, the model's outcome variable, and complete_aphant).
x_lab: Label for the x-axis. Default is "VVIQ score".
y_lab: Label for the y-axis. Default "Total TAS score" — override this explicitly when plotting a subscale model (e.g. "TAS DIF score"), since the default is not derived from the outcome variable automatically.
limits: Limits of the x-axis. Default is c(8, 81) to accomodate both the half-violin and stats on the left and the secondary axis on the right.
vviq_breaks: Breaks (ticks) for the VVIQ x-axis
tas_breaks: Breaks for the outcome variable (the main one being tas).
dot_size: Size of the individual above-floor data points. Default is 1.2.
dot_alpha: Transparency of the individual above-floor data points. Default is 0.4.
cross_size: Size of the cross at the end of the regression line. Default is 2.
cross_stroke: Stroke width of the cross marker. Default is 0.8.
violin_width: Half-width of the floor-group violin, in VVIQ-scale units. Default 3 (i.e. violin extends from VVIQ=16 to VVIQ=13).
stat_txt_size: Size for the floor effect text on the left.
xbar_label: Right-side "mean" label. Default is "Sample mean" (with a linebreak). Another former option was expression(bar(x)) to display a mathematical X-bar symbol.
xbar_face: Face of the right label. Default is "italic".
xbar_vjust: Vertical adjustment for the right-side "mean" label (formerly X-bar). Default is 0.5.
colorbar_width: Width of the colorbar in the legend in pt. Default is 14
mean_line_color: Colour of the sample-mean reference line (dashed horizontal line, labelled via the right-side X-bar axis). Default is "grey40".
mean_line_width: Line width of the sample-mean reference line. Default is 0.2.
floor_fill_color: Fill colour for the floor-group violin, jittered points, and mean/CI point-range. Default is "#C44E52" (a muted red).
floor_line_color: Line/outline colour for the floor-group violin border and mean/CI point-range. Default is "#8B3A3E" (a darker red).
floor_violin_alpha: Fill transparency of the floor-group violin. Default is 0.6.
floor_violin_linewidth: Border line width of the floor-group violin. Default is 0.2.
floor_violin_nudge: Horizontal nudge applied to the floor-group violin, in VVIQ-scale units (negative moves it further left of VVIQ=16). Default is -2.
floor_jitter_alpha: Transparency of the floor-group's individual jittered points. Default is 0.2.
floor_jitter_size: Size of the floor-group's individual jittered points. Default is 1.2.
floor_pointrange_linewidth: Line width of the floor-group's mean/CI point-range. Default is 0.5.
floor_pointrange_size: Point size of the floor-group's mean/CI point-range. Default is 0.4.
floor_guide_color: Colour of the dotted vertical guide line marking VVIQ=16, spanning the violin's range. Default is "grey82".
floor_guide_linewidth: Line width of the dotted vertical guide line at VVIQ=16. Default is 0.2.
floor_guide_y_pad: Additional downward padding (in outcome-scale units) below the violin's own range for the vertical guide line's lower end. Default is 5.
floor_label_x: Horizontal position (VVIQ-scale) of the "Floor VVIQ" text label. Default is 15.2.
floor_label_y: Vertical position (outcome-scale) of the "Floor VVIQ" text label. Default is 20.
floor_label_color: Colour of the "Floor VVIQ" text label. Default is "grey65".
floor_label_size: Text size of the "Floor VVIQ" text label. Default is 1.75.
arrow_x: Horizontal position (VVIQ-scale) of the two-way arrow and its connecting tick segments, marking the gap between the cross and the floor-group mean. Default is 10.5.
arrow_linewidth: Line width of the two-way arrow. Default is 0.3.
arrow_length: Length of the two-way arrow. Default is 0.05.
tick_linewidth: Line width of the two short horizontal dotted tick segments connecting the arrow's ends to the cross and floor-group mean. Default is 0.2.
stat_label_x: Horizontal position (VVIQ-scale) of the floor-effect statistics text label, to the left of the arrow. Default is 8.2.
stat_label_lineheight: Lineheight of the stat label (to tune the mandatory linebreak). Default is 0.9 (ggplot2's default).
fitted_line_color: Colour of the fitted above-floor regression line (both solid and dashed/extrapolated segments). Default is "black".
fitted_line_width: Line width of the solid, real-data-range portion of the fitted regression line. Default is 0.5.
extrap_line_width: Line width of the dashed, extrapolated portion of the fitted regression line. Default is 0.4.
base_theme: Base ggplot2 theme to use with theme_pdf() (default is ggplot2::theme_minimal).
axis_relative_size: A numeric value for the relative size of the axis text compared to the base size. The default is 0.85, which is slightly smaller than the base size.
axis_relative_x: Relative size of the x-axis text. Default is 1.
axis_relative_y: Relative size of the y-axis text. Default is 1.
...: Additional arguments passed to the theme_pdf() function for further customization of the plot theme.

Value

A ggplot2 object.