ShinyItemAnalysis (version 1.5.4)

plotCumulative: Plot cumulative and category probabilities of cumulative logit model

Description

Function for plotting cumulative and category probabilities function estimated by vglm() function from the VGAM package using the ggplot2 package.

Usage

plotCumulative(x, type = "cumulative", matching.name = "matching")

Value

An object of class ggplot and/or gg.

Arguments

x

object of class vglm

type

character: type of plot to be displayed. Options are "cumulative" (default) for cumulative probabilities and "category" for category probabilities.

matching.name

character: name of matching criterion used for estimation in x.

Author

Tomas Jurica
Institute of Computer Science of the Czech Academy of Sciences

Adela Hladka
Institute of Computer Science of the Czech Academy of Sciences

Patricia Martinkova
Institute of Computer Science of the Czech Academy of Sciences

See Also

VGAM::vglm()

Examples

# loading packages
library(VGAM)

# loading data
data(Science, package = "mirt")

# total score calculation
score <- rowSums(Science)
Science[, 1] <- factor(Science[, 1], levels = sort(unique(Science[, 1])), ordered = TRUE)

# cumulative logit model for item 1
fit <- vglm(Science[, 1] ~ score, family = cumulative(reverse = TRUE, parallel = TRUE))
# coefficients for item 1
coef(fit)

plotCumulative(fit, type = "cumulative", matching.name = "Total score")
plotCumulative(fit, type = "category", matching.name = "Total score")