RMplotStackedbar: Stacked Bar Chart of Item Response Distributions

In easyRasch2: Psychometric Analysis with Rasch Measurement Theory

Stacked Bar Chart of Item Response Distributions

Description

Creates a horizontal stacked bar chart showing the response distribution for all items. Each bar represents one item, with segments coloured by response category. Counts are displayed as text labels within each segment. This is a descriptive data visualization tool intended for use before model fitting.

Usage

RMplotStackedbar(
  data,
  item_labels = NULL,
  category_labels = NULL,
  show_n = TRUE,
  show_percent = FALSE,
  text_color = "sienna1",
  text_size = 3,
  min_label_n = 0L,
  viridis_option = "D",
  viridis_end = 0.99,
  title = "Item responses"
)

Arguments

data	A data.frame in wide format containing only the item response columns. Each column is one item, each row is one person. All columns must be numeric (integer-valued). Response categories may be coded starting from 0 or 1. Do not include person IDs, grouping variables, or other non-item columns.
item_labels	An optional character vector of descriptive labels for the items (y-axis). Must be the same length as ncol(data). If NULL (the default), column names are used.
category_labels	An optional character vector of labels for the response categories (legend). Must be the same length as the number of response categories spanning from the minimum to the maximum observed value, ordered from lowest to highest category. If NULL (the default), numeric category values are used.
show_n	Logical. If TRUE (the default), the count of responses is displayed as a text label inside each bar segment.
show_percent	Logical. If TRUE, the percentage of responses is displayed instead of (or in addition to) counts. Default is FALSE.
text_color	Character. Colour for the count/percentage labels. Default is "sienna1".
text_size	Numeric. Size of the count/percentage labels. Default is 3.
min_label_n	Integer. Minimum count required for a label to be displayed within a bar segment. Segments with fewer responses are left unlabelled to avoid clutter. Default is 0L (all segments labelled).
viridis_option	Character. Viridis palette option. One of "A" through "H". Default is "D".
viridis_end	Numeric in [0, 1]. End point of the viridis colour scale. Default is 0.99.
title	Character. Plot title. Default is "Item responses".

Details

Items are displayed on the y-axis in the same order as the columns in data (first column at the top). Each bar is divided into segments representing response categories, with the lowest category on the left and the highest on the right. The total bar length equals the number of non-missing responses for that item.

Categories with zero responses still appear in the legend but produce no visible bar segment, which helps identify gaps in the response distribution.

The plot caption reports the sample in the standard ⁠n = X respondents (policy)⁠ form; item-level NAs are retained – each bar counts the non-missing responses for that item.

Input requirements:

• All columns must be numeric (integer-valued).

• The data frame must contain at least 2 columns (items) and at least 1 row (person).

Value

A ggplot2::ggplot object.

See Also

RMplotBar(), RMplotTile()

Examples

if (requireNamespace("eRm", quietly = TRUE) &&
    requireNamespace("ggplot2", quietly = TRUE)) {
  data(pcmdat2, package = "eRm")

  # Basic stacked bar chart
  RMplotStackedbar(pcmdat2)

  # With custom item and category labels
  RMplotStackedbar(
    pcmdat2,
    item_labels     = c("Mood", "Sleep", "Appetite", "Energy"),
    category_labels = c("Never", "Sometimes", "Often")
  )

  # Show percentages, suppress small segments
  RMplotStackedbar(
    pcmdat2,
    show_percent = TRUE,
    show_n       = FALSE,
    min_label_n  = 5
  )
}

easyRasch2 documentation built on Sept. 13, 2026, 1:07 a.m.